<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <meta name="nodejs.org:node-version" content="v16.20.0"> <title>Web Streams API | Node.js v16.20.0 Documentation</title> <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> <link rel="stylesheet" href="assets/style.css"> <link rel="stylesheet" href="assets/hljs.css"> <link rel="canonical" href="https://nodejs.org/api/webstreams.html"> <script async defer src="assets/api.js" type="text/javascript"></script> <style>@media(max-width:358px){.with-17-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:350px){.with-16-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:654px){.with-54-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:334px){.with-14-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:718px){.with-62-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:622px){.with-50-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:638px){.with-52-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}@media(max-width:742px){.with-65-chars>.js-flavor-selector{float:none;margin:0 0 1em auto;}}</style> </head> <body class="alt apidoc" id="api-section-webstreams"> <div id="content" class="clearfix"> <div id="column2" class="interior"> <div id="intro" class="interior"> <a href="/" title="Go back to the home page"> Node.js </a> </div> <ul> <li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> <li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> </ul> <hr class="line"> <ul> <li><a href="assert.html" class="nav-assert">Assertion testing</a></li> <li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> <li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> <li><a href="buffer.html" class="nav-buffer">Buffer</a></li> <li><a href="addons.html" class="nav-addons">C++ addons</a></li> <li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> <li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> <li><a href="child_process.html" class="nav-child_process">Child processes</a></li> <li><a href="cluster.html" class="nav-cluster">Cluster</a></li> <li><a href="cli.html" class="nav-cli">Command-line options</a></li> <li><a href="console.html" class="nav-console">Console</a></li> <li><a href="corepack.html" class="nav-corepack">Corepack</a></li> <li><a href="crypto.html" class="nav-crypto">Crypto</a></li> <li><a href="debugger.html" class="nav-debugger">Debugger</a></li> <li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> <li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> <li><a href="dns.html" class="nav-dns">DNS</a></li> <li><a href="domain.html" class="nav-domain">Domain</a></li> <li><a href="errors.html" class="nav-errors">Errors</a></li> <li><a href="events.html" class="nav-events">Events</a></li> <li><a href="fs.html" class="nav-fs">File system</a></li> <li><a href="globals.html" class="nav-globals">Globals</a></li> <li><a href="http.html" class="nav-http">HTTP</a></li> <li><a href="http2.html" class="nav-http2">HTTP/2</a></li> <li><a href="https.html" class="nav-https">HTTPS</a></li> <li><a href="inspector.html" class="nav-inspector">Inspector</a></li> <li><a href="intl.html" class="nav-intl">Internationalization</a></li> <li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> <li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> <li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> <li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> <li><a href="net.html" class="nav-net">Net</a></li> <li><a href="os.html" class="nav-os">OS</a></li> <li><a href="path.html" class="nav-path">Path</a></li> <li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> <li><a href="permissions.html" class="nav-permissions">Permissions</a></li> <li><a href="process.html" class="nav-process">Process</a></li> <li><a href="punycode.html" class="nav-punycode">Punycode</a></li> <li><a href="querystring.html" class="nav-querystring">Query strings</a></li> <li><a href="readline.html" class="nav-readline">Readline</a></li> <li><a href="repl.html" class="nav-repl">REPL</a></li> <li><a href="report.html" class="nav-report">Report</a></li> <li><a href="stream.html" class="nav-stream">Stream</a></li> <li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> <li><a href="test.html" class="nav-test">Test runner</a></li> <li><a href="timers.html" class="nav-timers">Timers</a></li> <li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> <li><a href="tracing.html" class="nav-tracing">Trace events</a></li> <li><a href="tty.html" class="nav-tty">TTY</a></li> <li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> <li><a href="url.html" class="nav-url">URL</a></li> <li><a href="util.html" class="nav-util">Utilities</a></li> <li><a href="v8.html" class="nav-v8">V8</a></li> <li><a href="vm.html" class="nav-vm">VM</a></li> <li><a href="wasi.html" class="nav-wasi">WASI</a></li> <li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> <li><a href="webstreams.html" class="nav-webstreams active">Web Streams API</a></li> <li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> <li><a href="zlib.html" class="nav-zlib">Zlib</a></li> </ul> <hr class="line"> <ul> <li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> </ul> </div> <div id="column1" data-id="webstreams" class="interior"> <header class="header"> <div class="header-container"> <h1>Node.js v16.20.0 documentation</h1> <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> <path fill="none" d="M0 0h24v24H0z" /> <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> </svg> <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> <path d="M0 0h24v24H0z" fill="none" /> <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> </svg> </button> </div> <div id="gtoc"> <ul> <li class="pinned-header">Node.js v16.20.0</li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Table of contents </a> <div class="picker"><div class="toc"><ul> <li><span class="stability_1"><a href="#web-streams-api">Web Streams API</a></span> <ul> <li><a href="#overview">Overview</a> <ul> <li><a href="#example-readablestream">Example <code>ReadableStream</code></a></li> </ul> </li> <li><a href="#api">API</a> <ul> <li><a href="#class-readablestream">Class: <code>ReadableStream</code></a> <ul> <li><a href="#new-readablestreamunderlyingsource--strategy"><code>new ReadableStream([underlyingSource [, strategy]])</code></a></li> <li><a href="#readablestreamlocked"><code>readableStream.locked</code></a></li> <li><a href="#readablestreamcancelreason"><code>readableStream.cancel([reason])</code></a></li> <li><a href="#readablestreamgetreaderoptions"><code>readableStream.getReader([options])</code></a></li> <li><a href="#readablestreampipethroughtransform-options"><code>readableStream.pipeThrough(transform[, options])</code></a></li> <li><a href="#readablestreampipetodestination-options"><code>readableStream.pipeTo(destination, options)</code></a></li> <li><a href="#readablestreamtee"><code>readableStream.tee()</code></a></li> <li><a href="#readablestreamvaluesoptions"><code>readableStream.values([options])</code></a></li> <li><a href="#async-iteration">Async Iteration</a></li> <li><a href="#transferring-with-postmessage">Transferring with <code>postMessage()</code></a></li> </ul> </li> <li><a href="#class-readablestreamdefaultreader">Class: <code>ReadableStreamDefaultReader</code></a> <ul> <li><a href="#new-readablestreamdefaultreaderstream"><code>new ReadableStreamDefaultReader(stream)</code></a></li> <li><a href="#readablestreamdefaultreadercancelreason"><code>readableStreamDefaultReader.cancel([reason])</code></a></li> <li><a href="#readablestreamdefaultreaderclosed"><code>readableStreamDefaultReader.closed</code></a></li> <li><a href="#readablestreamdefaultreaderread"><code>readableStreamDefaultReader.read()</code></a></li> <li><a href="#readablestreamdefaultreaderreleaselock"><code>readableStreamDefaultReader.releaseLock()</code></a></li> </ul> </li> <li><a href="#class-readablestreambyobreader">Class: <code>ReadableStreamBYOBReader</code></a> <ul> <li><a href="#new-readablestreambyobreaderstream"><code>new ReadableStreamBYOBReader(stream)</code></a></li> <li><a href="#readablestreambyobreadercancelreason"><code>readableStreamBYOBReader.cancel([reason])</code></a></li> <li><a href="#readablestreambyobreaderclosed"><code>readableStreamBYOBReader.closed</code></a></li> <li><a href="#readablestreambyobreaderreadview"><code>readableStreamBYOBReader.read(view)</code></a></li> <li><a href="#readablestreambyobreaderreleaselock"><code>readableStreamBYOBReader.releaseLock()</code></a></li> </ul> </li> <li><a href="#class-readablestreamdefaultcontroller">Class: <code>ReadableStreamDefaultController</code></a> <ul> <li><a href="#readablestreamdefaultcontrollerclose"><code>readableStreamDefaultController.close()</code></a></li> <li><a href="#readablestreamdefaultcontrollerdesiredsize"><code>readableStreamDefaultController.desiredSize</code></a></li> <li><a href="#readablestreamdefaultcontrollerenqueuechunk"><code>readableStreamDefaultController.enqueue(chunk)</code></a></li> <li><a href="#readablestreamdefaultcontrollererrorerror"><code>readableStreamDefaultController.error(error)</code></a></li> </ul> </li> <li><a href="#class-readablebytestreamcontroller">Class: <code>ReadableByteStreamController</code></a> <ul> <li><a href="#readablebytestreamcontrollerbyobrequest"><code>readableByteStreamController.byobRequest</code></a></li> <li><a href="#readablebytestreamcontrollerclose"><code>readableByteStreamController.close()</code></a></li> <li><a href="#readablebytestreamcontrollerdesiredsize"><code>readableByteStreamController.desiredSize</code></a></li> <li><a href="#readablebytestreamcontrollerenqueuechunk"><code>readableByteStreamController.enqueue(chunk)</code></a></li> <li><a href="#readablebytestreamcontrollererrorerror"><code>readableByteStreamController.error(error)</code></a></li> </ul> </li> <li><a href="#class-readablestreambyobrequest">Class: <code>ReadableStreamBYOBRequest</code></a> <ul> <li><a href="#readablestreambyobrequestrespondbyteswritten"><code>readableStreamBYOBRequest.respond(bytesWritten)</code></a></li> <li><a href="#readablestreambyobrequestrespondwithnewviewview"><code>readableStreamBYOBRequest.respondWithNewView(view)</code></a></li> <li><a href="#readablestreambyobrequestview"><code>readableStreamBYOBRequest.view</code></a></li> </ul> </li> <li><a href="#class-writablestream">Class: <code>WritableStream</code></a> <ul> <li><a href="#new-writablestreamunderlyingsink-strategy"><code>new WritableStream([underlyingSink[, strategy]])</code></a></li> <li><a href="#writablestreamabortreason"><code>writableStream.abort([reason])</code></a></li> <li><a href="#writablestreamclose"><code>writableStream.close()</code></a></li> <li><a href="#writablestreamgetwriter"><code>writableStream.getWriter()</code></a></li> <li><a href="#writablestreamlocked"><code>writableStream.locked</code></a></li> <li><a href="#transferring-with-postmessage_1">Transferring with postMessage()</a></li> </ul> </li> <li><a href="#class-writablestreamdefaultwriter">Class: <code>WritableStreamDefaultWriter</code></a> <ul> <li><a href="#new-writablestreamdefaultwriterstream"><code>new WritableStreamDefaultWriter(stream)</code></a></li> <li><a href="#writablestreamdefaultwriterabortreason"><code>writableStreamDefaultWriter.abort([reason])</code></a></li> <li><a href="#writablestreamdefaultwriterclose"><code>writableStreamDefaultWriter.close()</code></a></li> <li><a href="#writablestreamdefaultwriterclosed"><code>writableStreamDefaultWriter.closed</code></a></li> <li><a href="#writablestreamdefaultwriterdesiredsize"><code>writableStreamDefaultWriter.desiredSize</code></a></li> <li><a href="#writablestreamdefaultwriterready"><code>writableStreamDefaultWriter.ready</code></a></li> <li><a href="#writablestreamdefaultwriterreleaselock"><code>writableStreamDefaultWriter.releaseLock()</code></a></li> <li><a href="#writablestreamdefaultwriterwritechunk"><code>writableStreamDefaultWriter.write([chunk])</code></a></li> </ul> </li> <li><a href="#class-writablestreamdefaultcontroller">Class: <code>WritableStreamDefaultController</code></a> <ul> <li><a href="#writablestreamdefaultcontrollerabortreason"><code>writableStreamDefaultController.abortReason</code></a></li> <li><a href="#writablestreamdefaultcontrollererrorerror"><code>writableStreamDefaultController.error(error)</code></a></li> <li><a href="#writablestreamdefaultcontrollersignal"><code>writableStreamDefaultController.signal</code></a></li> </ul> </li> <li><a href="#class-transformstream">Class: <code>TransformStream</code></a> <ul> <li><a href="#new-transformstreamtransformer-writablestrategy-readablestrategy"><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code></a></li> <li><a href="#transformstreamreadable"><code>transformStream.readable</code></a></li> <li><a href="#transformstreamwritable"><code>transformStream.writable</code></a></li> <li><a href="#transferring-with-postmessage_2">Transferring with postMessage()</a></li> </ul> </li> <li><a href="#class-transformstreamdefaultcontroller">Class: <code>TransformStreamDefaultController</code></a> <ul> <li><a href="#transformstreamdefaultcontrollerdesiredsize"><code>transformStreamDefaultController.desiredSize</code></a></li> <li><a href="#transformstreamdefaultcontrollerenqueuechunk"><code>transformStreamDefaultController.enqueue([chunk])</code></a></li> <li><a href="#transformstreamdefaultcontrollererrorreason"><code>transformStreamDefaultController.error([reason])</code></a></li> <li><a href="#transformstreamdefaultcontrollerterminate"><code>transformStreamDefaultController.terminate()</code></a></li> </ul> </li> <li><a href="#class-bytelengthqueuingstrategy">Class: <code>ByteLengthQueuingStrategy</code></a> <ul> <li><a href="#new-bytelengthqueuingstrategyoptions"><code>new ByteLengthQueuingStrategy(options)</code></a></li> <li><a href="#bytelengthqueuingstrategyhighwatermark"><code>byteLengthQueuingStrategy.highWaterMark</code></a></li> <li><a href="#bytelengthqueuingstrategysize"><code>byteLengthQueuingStrategy.size</code></a></li> </ul> </li> <li><a href="#class-countqueuingstrategy">Class: <code>CountQueuingStrategy</code></a> <ul> <li><a href="#new-countqueuingstrategyoptions"><code>new CountQueuingStrategy(options)</code></a></li> <li><a href="#countqueuingstrategyhighwatermark"><code>countQueuingStrategy.highWaterMark</code></a></li> <li><a href="#countqueuingstrategysize"><code>countQueuingStrategy.size</code></a></li> </ul> </li> <li><a href="#class-textencoderstream">Class: <code>TextEncoderStream</code></a> <ul> <li><a href="#new-textencoderstream"><code>new TextEncoderStream()</code></a></li> <li><a href="#textencoderstreamencoding"><code>textEncoderStream.encoding</code></a></li> <li><a href="#textencoderstreamreadable"><code>textEncoderStream.readable</code></a></li> <li><a href="#textencoderstreamwritable"><code>textEncoderStream.writable</code></a></li> </ul> </li> <li><a href="#class-textdecoderstream">Class: <code>TextDecoderStream</code></a> <ul> <li><a href="#new-textdecoderstreamencoding-options"><code>new TextDecoderStream([encoding[, options]])</code></a></li> <li><a href="#textdecoderstreamencoding"><code>textDecoderStream.encoding</code></a></li> <li><a href="#textdecoderstreamfatal"><code>textDecoderStream.fatal</code></a></li> <li><a href="#textdecoderstreamignorebom"><code>textDecoderStream.ignoreBOM</code></a></li> <li><a href="#textdecoderstreamreadable"><code>textDecoderStream.readable</code></a></li> <li><a href="#textdecoderstreamwritable"><code>textDecoderStream.writable</code></a></li> </ul> </li> <li><a href="#utility-consumers">Utility Consumers</a> <ul> <li><a href="#streamconsumersarraybufferstream"><code>streamConsumers.arrayBuffer(stream)</code></a></li> <li><a href="#streamconsumersblobstream"><code>streamConsumers.blob(stream)</code></a></li> <li><a href="#streamconsumersbufferstream"><code>streamConsumers.buffer(stream)</code></a></li> <li><a href="#streamconsumersjsonstream"><code>streamConsumers.json(stream)</code></a></li> <li><a href="#streamconsumerstextstream"><code>streamConsumers.text(stream)</code></a></li> </ul> </li> </ul> </li> </ul> </li> </ul></div></div> </li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Index </a> <div class="picker"><ul> <li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> <li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> <li> <a href="index.html">Index</a> </li> </ul> <hr class="line"> <ul> <li><a href="assert.html" class="nav-assert">Assertion testing</a></li> <li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> <li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> <li><a href="buffer.html" class="nav-buffer">Buffer</a></li> <li><a href="addons.html" class="nav-addons">C++ addons</a></li> <li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> <li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> <li><a href="child_process.html" class="nav-child_process">Child processes</a></li> <li><a href="cluster.html" class="nav-cluster">Cluster</a></li> <li><a href="cli.html" class="nav-cli">Command-line options</a></li> <li><a href="console.html" class="nav-console">Console</a></li> <li><a href="corepack.html" class="nav-corepack">Corepack</a></li> <li><a href="crypto.html" class="nav-crypto">Crypto</a></li> <li><a href="debugger.html" class="nav-debugger">Debugger</a></li> <li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> <li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> <li><a href="dns.html" class="nav-dns">DNS</a></li> <li><a href="domain.html" class="nav-domain">Domain</a></li> <li><a href="errors.html" class="nav-errors">Errors</a></li> <li><a href="events.html" class="nav-events">Events</a></li> <li><a href="fs.html" class="nav-fs">File system</a></li> <li><a href="globals.html" class="nav-globals">Globals</a></li> <li><a href="http.html" class="nav-http">HTTP</a></li> <li><a href="http2.html" class="nav-http2">HTTP/2</a></li> <li><a href="https.html" class="nav-https">HTTPS</a></li> <li><a href="inspector.html" class="nav-inspector">Inspector</a></li> <li><a href="intl.html" class="nav-intl">Internationalization</a></li> <li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> <li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> <li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> <li><a href="packages.html" class="nav-packages">Modules: Packages</a></li> <li><a href="net.html" class="nav-net">Net</a></li> <li><a href="os.html" class="nav-os">OS</a></li> <li><a href="path.html" class="nav-path">Path</a></li> <li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> <li><a href="permissions.html" class="nav-permissions">Permissions</a></li> <li><a href="process.html" class="nav-process">Process</a></li> <li><a href="punycode.html" class="nav-punycode">Punycode</a></li> <li><a href="querystring.html" class="nav-querystring">Query strings</a></li> <li><a href="readline.html" class="nav-readline">Readline</a></li> <li><a href="repl.html" class="nav-repl">REPL</a></li> <li><a href="report.html" class="nav-report">Report</a></li> <li><a href="stream.html" class="nav-stream">Stream</a></li> <li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> <li><a href="test.html" class="nav-test">Test runner</a></li> <li><a href="timers.html" class="nav-timers">Timers</a></li> <li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> <li><a href="tracing.html" class="nav-tracing">Trace events</a></li> <li><a href="tty.html" class="nav-tty">TTY</a></li> <li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> <li><a href="url.html" class="nav-url">URL</a></li> <li><a href="util.html" class="nav-util">Utilities</a></li> <li><a href="v8.html" class="nav-v8">V8</a></li> <li><a href="vm.html" class="nav-vm">VM</a></li> <li><a href="wasi.html" class="nav-wasi">WASI</a></li> <li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> <li><a href="webstreams.html" class="nav-webstreams active">Web Streams API</a></li> <li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> <li><a href="zlib.html" class="nav-zlib">Zlib</a></li> </ul> <hr class="line"> <ul> <li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> </ul></div> </li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Other versions </a> <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v19.x/api/webstreams.html">19.x</a></li> <li><a href="https://nodejs.org/docs/latest-v18.x/api/webstreams.html">18.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v17.x/api/webstreams.html">17.x</a></li> <li><a href="https://nodejs.org/docs/latest-v16.x/api/webstreams.html">16.x <b>LTS</b></a></li></ol></div> </li> <li class="picker-header"> <a href="#"> <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> Options </a> <div class="picker"> <ul> <li> <a href="all.html">View on single page</a> </li> <li> <a href="webstreams.json">View as JSON</a> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/webstreams.md">Edit on GitHub</a></li> </ul> </div> </li> </ul> </div> <hr> </header> <details id="toc" open><summary>Table of contents</summary><ul> <li><span class="stability_1"><a href="#web-streams-api">Web Streams API</a></span> <ul> <li><a href="#overview">Overview</a> <ul> <li><a href="#example-readablestream">Example <code>ReadableStream</code></a></li> </ul> </li> <li><a href="#api">API</a> <ul> <li><a href="#class-readablestream">Class: <code>ReadableStream</code></a> <ul> <li><a href="#new-readablestreamunderlyingsource--strategy"><code>new ReadableStream([underlyingSource [, strategy]])</code></a></li> <li><a href="#readablestreamlocked"><code>readableStream.locked</code></a></li> <li><a href="#readablestreamcancelreason"><code>readableStream.cancel([reason])</code></a></li> <li><a href="#readablestreamgetreaderoptions"><code>readableStream.getReader([options])</code></a></li> <li><a href="#readablestreampipethroughtransform-options"><code>readableStream.pipeThrough(transform[, options])</code></a></li> <li><a href="#readablestreampipetodestination-options"><code>readableStream.pipeTo(destination, options)</code></a></li> <li><a href="#readablestreamtee"><code>readableStream.tee()</code></a></li> <li><a href="#readablestreamvaluesoptions"><code>readableStream.values([options])</code></a></li> <li><a href="#async-iteration">Async Iteration</a></li> <li><a href="#transferring-with-postmessage">Transferring with <code>postMessage()</code></a></li> </ul> </li> <li><a href="#class-readablestreamdefaultreader">Class: <code>ReadableStreamDefaultReader</code></a> <ul> <li><a href="#new-readablestreamdefaultreaderstream"><code>new ReadableStreamDefaultReader(stream)</code></a></li> <li><a href="#readablestreamdefaultreadercancelreason"><code>readableStreamDefaultReader.cancel([reason])</code></a></li> <li><a href="#readablestreamdefaultreaderclosed"><code>readableStreamDefaultReader.closed</code></a></li> <li><a href="#readablestreamdefaultreaderread"><code>readableStreamDefaultReader.read()</code></a></li> <li><a href="#readablestreamdefaultreaderreleaselock"><code>readableStreamDefaultReader.releaseLock()</code></a></li> </ul> </li> <li><a href="#class-readablestreambyobreader">Class: <code>ReadableStreamBYOBReader</code></a> <ul> <li><a href="#new-readablestreambyobreaderstream"><code>new ReadableStreamBYOBReader(stream)</code></a></li> <li><a href="#readablestreambyobreadercancelreason"><code>readableStreamBYOBReader.cancel([reason])</code></a></li> <li><a href="#readablestreambyobreaderclosed"><code>readableStreamBYOBReader.closed</code></a></li> <li><a href="#readablestreambyobreaderreadview"><code>readableStreamBYOBReader.read(view)</code></a></li> <li><a href="#readablestreambyobreaderreleaselock"><code>readableStreamBYOBReader.releaseLock()</code></a></li> </ul> </li> <li><a href="#class-readablestreamdefaultcontroller">Class: <code>ReadableStreamDefaultController</code></a> <ul> <li><a href="#readablestreamdefaultcontrollerclose"><code>readableStreamDefaultController.close()</code></a></li> <li><a href="#readablestreamdefaultcontrollerdesiredsize"><code>readableStreamDefaultController.desiredSize</code></a></li> <li><a href="#readablestreamdefaultcontrollerenqueuechunk"><code>readableStreamDefaultController.enqueue(chunk)</code></a></li> <li><a href="#readablestreamdefaultcontrollererrorerror"><code>readableStreamDefaultController.error(error)</code></a></li> </ul> </li> <li><a href="#class-readablebytestreamcontroller">Class: <code>ReadableByteStreamController</code></a> <ul> <li><a href="#readablebytestreamcontrollerbyobrequest"><code>readableByteStreamController.byobRequest</code></a></li> <li><a href="#readablebytestreamcontrollerclose"><code>readableByteStreamController.close()</code></a></li> <li><a href="#readablebytestreamcontrollerdesiredsize"><code>readableByteStreamController.desiredSize</code></a></li> <li><a href="#readablebytestreamcontrollerenqueuechunk"><code>readableByteStreamController.enqueue(chunk)</code></a></li> <li><a href="#readablebytestreamcontrollererrorerror"><code>readableByteStreamController.error(error)</code></a></li> </ul> </li> <li><a href="#class-readablestreambyobrequest">Class: <code>ReadableStreamBYOBRequest</code></a> <ul> <li><a href="#readablestreambyobrequestrespondbyteswritten"><code>readableStreamBYOBRequest.respond(bytesWritten)</code></a></li> <li><a href="#readablestreambyobrequestrespondwithnewviewview"><code>readableStreamBYOBRequest.respondWithNewView(view)</code></a></li> <li><a href="#readablestreambyobrequestview"><code>readableStreamBYOBRequest.view</code></a></li> </ul> </li> <li><a href="#class-writablestream">Class: <code>WritableStream</code></a> <ul> <li><a href="#new-writablestreamunderlyingsink-strategy"><code>new WritableStream([underlyingSink[, strategy]])</code></a></li> <li><a href="#writablestreamabortreason"><code>writableStream.abort([reason])</code></a></li> <li><a href="#writablestreamclose"><code>writableStream.close()</code></a></li> <li><a href="#writablestreamgetwriter"><code>writableStream.getWriter()</code></a></li> <li><a href="#writablestreamlocked"><code>writableStream.locked</code></a></li> <li><a href="#transferring-with-postmessage_1">Transferring with postMessage()</a></li> </ul> </li> <li><a href="#class-writablestreamdefaultwriter">Class: <code>WritableStreamDefaultWriter</code></a> <ul> <li><a href="#new-writablestreamdefaultwriterstream"><code>new WritableStreamDefaultWriter(stream)</code></a></li> <li><a href="#writablestreamdefaultwriterabortreason"><code>writableStreamDefaultWriter.abort([reason])</code></a></li> <li><a href="#writablestreamdefaultwriterclose"><code>writableStreamDefaultWriter.close()</code></a></li> <li><a href="#writablestreamdefaultwriterclosed"><code>writableStreamDefaultWriter.closed</code></a></li> <li><a href="#writablestreamdefaultwriterdesiredsize"><code>writableStreamDefaultWriter.desiredSize</code></a></li> <li><a href="#writablestreamdefaultwriterready"><code>writableStreamDefaultWriter.ready</code></a></li> <li><a href="#writablestreamdefaultwriterreleaselock"><code>writableStreamDefaultWriter.releaseLock()</code></a></li> <li><a href="#writablestreamdefaultwriterwritechunk"><code>writableStreamDefaultWriter.write([chunk])</code></a></li> </ul> </li> <li><a href="#class-writablestreamdefaultcontroller">Class: <code>WritableStreamDefaultController</code></a> <ul> <li><a href="#writablestreamdefaultcontrollerabortreason"><code>writableStreamDefaultController.abortReason</code></a></li> <li><a href="#writablestreamdefaultcontrollererrorerror"><code>writableStreamDefaultController.error(error)</code></a></li> <li><a href="#writablestreamdefaultcontrollersignal"><code>writableStreamDefaultController.signal</code></a></li> </ul> </li> <li><a href="#class-transformstream">Class: <code>TransformStream</code></a> <ul> <li><a href="#new-transformstreamtransformer-writablestrategy-readablestrategy"><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code></a></li> <li><a href="#transformstreamreadable"><code>transformStream.readable</code></a></li> <li><a href="#transformstreamwritable"><code>transformStream.writable</code></a></li> <li><a href="#transferring-with-postmessage_2">Transferring with postMessage()</a></li> </ul> </li> <li><a href="#class-transformstreamdefaultcontroller">Class: <code>TransformStreamDefaultController</code></a> <ul> <li><a href="#transformstreamdefaultcontrollerdesiredsize"><code>transformStreamDefaultController.desiredSize</code></a></li> <li><a href="#transformstreamdefaultcontrollerenqueuechunk"><code>transformStreamDefaultController.enqueue([chunk])</code></a></li> <li><a href="#transformstreamdefaultcontrollererrorreason"><code>transformStreamDefaultController.error([reason])</code></a></li> <li><a href="#transformstreamdefaultcontrollerterminate"><code>transformStreamDefaultController.terminate()</code></a></li> </ul> </li> <li><a href="#class-bytelengthqueuingstrategy">Class: <code>ByteLengthQueuingStrategy</code></a> <ul> <li><a href="#new-bytelengthqueuingstrategyoptions"><code>new ByteLengthQueuingStrategy(options)</code></a></li> <li><a href="#bytelengthqueuingstrategyhighwatermark"><code>byteLengthQueuingStrategy.highWaterMark</code></a></li> <li><a href="#bytelengthqueuingstrategysize"><code>byteLengthQueuingStrategy.size</code></a></li> </ul> </li> <li><a href="#class-countqueuingstrategy">Class: <code>CountQueuingStrategy</code></a> <ul> <li><a href="#new-countqueuingstrategyoptions"><code>new CountQueuingStrategy(options)</code></a></li> <li><a href="#countqueuingstrategyhighwatermark"><code>countQueuingStrategy.highWaterMark</code></a></li> <li><a href="#countqueuingstrategysize"><code>countQueuingStrategy.size</code></a></li> </ul> </li> <li><a href="#class-textencoderstream">Class: <code>TextEncoderStream</code></a> <ul> <li><a href="#new-textencoderstream"><code>new TextEncoderStream()</code></a></li> <li><a href="#textencoderstreamencoding"><code>textEncoderStream.encoding</code></a></li> <li><a href="#textencoderstreamreadable"><code>textEncoderStream.readable</code></a></li> <li><a href="#textencoderstreamwritable"><code>textEncoderStream.writable</code></a></li> </ul> </li> <li><a href="#class-textdecoderstream">Class: <code>TextDecoderStream</code></a> <ul> <li><a href="#new-textdecoderstreamencoding-options"><code>new TextDecoderStream([encoding[, options]])</code></a></li> <li><a href="#textdecoderstreamencoding"><code>textDecoderStream.encoding</code></a></li> <li><a href="#textdecoderstreamfatal"><code>textDecoderStream.fatal</code></a></li> <li><a href="#textdecoderstreamignorebom"><code>textDecoderStream.ignoreBOM</code></a></li> <li><a href="#textdecoderstreamreadable"><code>textDecoderStream.readable</code></a></li> <li><a href="#textdecoderstreamwritable"><code>textDecoderStream.writable</code></a></li> </ul> </li> <li><a href="#utility-consumers">Utility Consumers</a> <ul> <li><a href="#streamconsumersarraybufferstream"><code>streamConsumers.arrayBuffer(stream)</code></a></li> <li><a href="#streamconsumersblobstream"><code>streamConsumers.blob(stream)</code></a></li> <li><a href="#streamconsumersbufferstream"><code>streamConsumers.buffer(stream)</code></a></li> <li><a href="#streamconsumersjsonstream"><code>streamConsumers.json(stream)</code></a></li> <li><a href="#streamconsumerstextstream"><code>streamConsumers.text(stream)</code></a></li> </ul> </li> </ul> </li> </ul> </li> </ul></details> <div id="apicontent"> <h2>Web Streams API<span><a class="mark" href="#web-streams-api" id="web-streams-api">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_web_streams_api"></a></h2> <p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> <p>An implementation of the <a href="https://streams.spec.whatwg.org/">WHATWG Streams Standard</a>.</p> <pre class="with-17-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">ReadableStream</span>, <span class="hljs-title class_">WritableStream</span>, <span class="hljs-title class_">TransformStream</span>, } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">ReadableStream</span>, <span class="hljs-title class_">WritableStream</span>, <span class="hljs-title class_">TransformStream</span>, } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'stream/web'</span>);</code></pre> <section><h3>Overview<span><a class="mark" href="#overview" id="overview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_overview"></a></h3> <p>The <a href="https://streams.spec.whatwg.org/">WHATWG Streams Standard</a> (or "web streams") defines an API for handling streaming data. It is similar to the Node.js <a href="stream.html">Streams</a> API but emerged later and has become the "standard" API for streaming data across many JavaScript environments.</p> <p>There are three primary types of objects:</p> <ul> <li><code>ReadableStream</code> - Represents a source of streaming data.</li> <li><code>WritableStream</code> - Represents a destination for streaming data.</li> <li><code>TransformStream</code> - Represents an algorithm for transforming streaming data.</li> </ul> <h4>Example <code>ReadableStream</code><span><a class="mark" href="#example-readablestream" id="example-readablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_example_readablestream"></a></h4> <p>This example creates a simple <code>ReadableStream</code> that pushes the current <code>performance.now()</code> timestamp once every second forever. An async iterable is used to read the data from the stream.</p> <pre class="with-16-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">ReadableStream</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-built_in">setInterval</span> <span class="hljs-keyword">as</span> every } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:timers/promises'</span>; <span class="hljs-keyword">import</span> { performance } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:perf_hooks'</span>; <span class="hljs-keyword">const</span> <span class="hljs-variable constant_">SECOND</span> = <span class="hljs-number">1000</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>({ <span class="hljs-keyword">async</span> <span class="hljs-title function_">start</span>(<span class="hljs-params">controller</span>) { <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> _ <span class="hljs-keyword">of</span> <span class="hljs-title function_">every</span>(<span class="hljs-variable constant_">SECOND</span>)) controller.<span class="hljs-title function_">enqueue</span>(performance.<span class="hljs-title function_">now</span>()); } }); <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> value <span class="hljs-keyword">of</span> stream) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(value);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">ReadableStream</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/web'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-attr">setInterval</span>: every } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:timers/promises'</span>); <span class="hljs-keyword">const</span> { performance } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); <span class="hljs-keyword">const</span> <span class="hljs-variable constant_">SECOND</span> = <span class="hljs-number">1000</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>({ <span class="hljs-keyword">async</span> <span class="hljs-title function_">start</span>(<span class="hljs-params">controller</span>) { <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> _ <span class="hljs-keyword">of</span> <span class="hljs-title function_">every</span>(<span class="hljs-variable constant_">SECOND</span>)) controller.<span class="hljs-title function_">enqueue</span>(performance.<span class="hljs-title function_">now</span>()); } }); (<span class="hljs-keyword">async</span> () => { <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> value <span class="hljs-keyword">of</span> stream) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(value); })();</code></pre> </section><section><h3>API<span><a class="mark" href="#api" id="api">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_api"></a></h3> <h4>Class: <code>ReadableStream</code><span><a class="mark" href="#class-readablestream" id="class-readablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestream"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <h5><code>new ReadableStream([underlyingSource [, strategy]])</code><span><a class="mark" href="#new-readablestreamunderlyingsource--strategy" id="new-readablestreamunderlyingsource--strategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestream_underlyingsource_strategy"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <!--lint disable maximum-line-length remark-lint--> <ul> <li><code>underlyingSource</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the <code>ReadableStream</code> is created. <ul> <li><code>controller</code> <a href="webstreams.html#class-readablestreamdefaultcontroller" class="type"><ReadableStreamDefaultController></a> | <a href="webstreams.html#class-readablebytestreamcontroller" class="type"><ReadableByteStreamController></a></li> <li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>pull</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called repeatedly when the <code>ReadableStream</code> internal queue is not full. The operation may be sync or async. If async, the function will not be called again until the previously returned promise is fulfilled. <ul> <li><code>controller</code> <a href="webstreams.html#class-readablestreamdefaultcontroller" class="type"><ReadableStreamDefaultController></a> | <a href="webstreams.html#class-readablebytestreamcontroller" class="type"><ReadableByteStreamController></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>cancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the <code>ReadableStream</code> is canceled. <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Must be <code>'bytes'</code> or <code>undefined</code>.</li> <li><code>autoAllocateChunkSize</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Used only when <code>type</code> is equal to <code>'bytes'</code>.</li> </ul> </li> <li><code>strategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.</li> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> </li> </ul> <!--lint enable maximum-line-length remark-lint--> <h5><code>readableStream.locked</code><span><a class="mark" href="#readablestreamlocked" id="readablestreamlocked">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_locked"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> Set to <code>true</code> if there is an active reader for this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</li> </ul> <p>The <code>readableStream.locked</code> property is <code>false</code> by default, and is switched to <code>true</code> while there is an active reader consuming the stream's data.</p> <h5><code>readableStream.cancel([reason])</code><span><a class="mark" href="#readablestreamcancelreason" id="readablestreamcancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_cancel_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code> once cancelation has been completed.</li> </ul> <h5><code>readableStream.getReader([options])</code><span><a class="mark" href="#readablestreamgetreaderoptions" id="readablestreamgetreaderoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_getreader_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>mode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> <code>'byob'</code> or <code>undefined</code></li> </ul> </li> <li>Returns: <a href="webstreams.html#class-readablestreamdefaultreader" class="type"><ReadableStreamDefaultReader></a> | <a href="webstreams.html#class-readablestreambyobreader" class="type"><ReadableStreamBYOBReader></a></li> </ul> <pre class="with-54-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">ReadableStream</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(); <span class="hljs-keyword">const</span> reader = stream.<span class="hljs-title function_">getReader</span>(); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-keyword">await</span> reader.<span class="hljs-title function_">read</span>());</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">ReadableStream</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/web'</span>); <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(); <span class="hljs-keyword">const</span> reader = stream.<span class="hljs-title function_">getReader</span>(); reader.<span class="hljs-title function_">read</span>().<span class="hljs-title function_">then</span>(<span class="hljs-variable language_">console</span>.<span class="hljs-property">log</span>);</code></pre> <p>Causes the <code>readableStream.locked</code> to be <code>true</code>.</p> <h5><code>readableStream.pipeThrough(transform[, options])</code><span><a class="mark" href="#readablestreampipethroughtransform-options" id="readablestreampipethroughtransform-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_pipethrough_transform_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>transform</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>readable</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> The <code>ReadableStream</code> to which <code>transform.writable</code> will push the potentially modified data is receives from this <code>ReadableStream</code>.</li> <li><code>writable</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> The <code>WritableStream</code> to which this <code>ReadableStream</code>'s data will be written.</li> </ul> </li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>preventAbort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in this <code>ReadableStream</code> will not cause <code>transform.writable</code> to be aborted.</li> <li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in the destination <code>transform.writable</code> do not cause this <code>ReadableStream</code> to be canceled.</li> <li><code>preventClose</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, closing this <code>ReadableStream</code> does not cause <code>transform.writable</code> to be closed.</li> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.</li> </ul> </li> <li>Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> From <code>transform.readable</code>.</li> </ul> <p>Connects this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to the pair of <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> provided in the <code>transform</code> argument such that the data from this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is written in to <code>transform.writable</code>, possibly transformed, then pushed to <code>transform.readable</code>. Once the pipeline is configured, <code>transform.readable</code> is returned.</p> <p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the pipe operation is active.</p> <pre class="with-17-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">ReadableStream</span>, <span class="hljs-title class_">TransformStream</span>, } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>({ <span class="hljs-title function_">start</span>(<span class="hljs-params">controller</span>) { controller.<span class="hljs-title function_">enqueue</span>(<span class="hljs-string">'a'</span>); }, }); <span class="hljs-keyword">const</span> transform = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TransformStream</span>({ <span class="hljs-title function_">transform</span>(<span class="hljs-params">chunk, controller</span>) { controller.<span class="hljs-title function_">enqueue</span>(chunk.<span class="hljs-title function_">toUpperCase</span>()); } }); <span class="hljs-keyword">const</span> transformedStream = stream.<span class="hljs-title function_">pipeThrough</span>(transform); <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> chunk <span class="hljs-keyword">of</span> transformedStream) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(chunk);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">ReadableStream</span>, <span class="hljs-title class_">TransformStream</span>, } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/web'</span>); <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>({ <span class="hljs-title function_">start</span>(<span class="hljs-params">controller</span>) { controller.<span class="hljs-title function_">enqueue</span>(<span class="hljs-string">'a'</span>); }, }); <span class="hljs-keyword">const</span> transform = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TransformStream</span>({ <span class="hljs-title function_">transform</span>(<span class="hljs-params">chunk, controller</span>) { controller.<span class="hljs-title function_">enqueue</span>(chunk.<span class="hljs-title function_">toUpperCase</span>()); } }); <span class="hljs-keyword">const</span> transformedStream = stream.<span class="hljs-title function_">pipeThrough</span>(transform); (<span class="hljs-keyword">async</span> () => { <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> chunk <span class="hljs-keyword">of</span> transformedStream) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(chunk); })();</code></pre> <h5><code>readableStream.pipeTo(destination, options)</code><span><a class="mark" href="#readablestreampipetodestination-options" id="readablestreampipetodestination-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_pipeto_destination_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>destination</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> to which this <code>ReadableStream</code>'s data will be written.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>preventAbort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in this <code>ReadableStream</code> will not cause <code>destination</code> to be aborted.</li> <li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, errors in the <code>destination</code> will not cause this <code>ReadableStream</code> to be canceled.</li> <li><code>preventClose</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, closing this <code>ReadableStream</code> does not cause <code>destination</code> to be closed.</li> <li><code>signal</code> <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.</li> </ul> </li> <li>Returns: A promise fulfilled with <code>undefined</code></li> </ul> <p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the pipe operation is active.</p> <h5><code>readableStream.tee()</code><span><a class="mark" href="#readablestreamtee" id="readablestreamtee">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_tee"></a></h5> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v16.18.0</td> <td><p>Support teeing a readable byte stream.</p></td></tr> <tr><td>v16.5.0</td> <td><p><span>Added in: v16.5.0</span></p></td></tr> </tbody></table> </details> </div> <ul> <li>Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream[]></a></li> </ul> <p>Returns a pair of new <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instances to which this <code>ReadableStream</code>'s data will be forwarded. Each will receive the same data.</p> <p>Causes the <code>readableStream.locked</code> to be <code>true</code>.</p> <h5><code>readableStream.values([options])</code><span><a class="mark" href="#readablestreamvaluesoptions" id="readablestreamvaluesoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestream_values_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>preventCancel</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, prevents the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> from being closed when the async iterator abruptly terminates. <strong>Default</strong>: <code>false</code>.</li> </ul> </li> </ul> <p>Creates and returns an async iterator usable for consuming this <code>ReadableStream</code>'s data.</p> <p>Causes the <code>readableStream.locked</code> to be <code>true</code> while the async iterator is active.</p> <pre><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(<span class="hljs-title function_">getSomeSource</span>()); <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> chunk <span class="hljs-keyword">of</span> stream.<span class="hljs-title function_">values</span>({ <span class="hljs-attr">preventCancel</span>: <span class="hljs-literal">true</span> })) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(chunk).<span class="hljs-title function_">toString</span>());</code></pre> <h5>Async Iteration<span><a class="mark" href="#async-iteration" id="async-iteration">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_async_iteration"></a></h5> <p>The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> object supports the async iterator protocol using <code>for await</code> syntax.</p> <pre><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(<span class="hljs-title function_">getSomeSource</span>()); <span class="hljs-keyword">for</span> <span class="hljs-keyword">await</span> (<span class="hljs-keyword">const</span> chunk <span class="hljs-keyword">of</span> stream) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(chunk).<span class="hljs-title function_">toString</span>());</code></pre> <p>The async iterator will consume the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> until it terminates.</p> <p>By default, if the async iterator exits early (via either a <code>break</code>, <code>return</code>, or a <code>throw</code>), the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be closed. To prevent automatic closing of the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>, use the <code>readableStream.values()</code> method to acquire the async iterator and set the <code>preventCancel</code> option to <code>true</code>.</p> <p>The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> must not be locked (that is, it must not have an existing active reader). During the async iteration, the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be locked.</p> <h5>Transferring with <code>postMessage()</code><span><a class="mark" href="#transferring-with-postmessage" id="transferring-with-postmessage">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage"></a></h5> <p>A <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(<span class="hljs-title function_">getReadableSourceSomehow</span>()); <span class="hljs-keyword">const</span> { port1, port2 } = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MessageChannel</span>(); port1.<span class="hljs-property">onmessage</span> = <span class="hljs-function">(<span class="hljs-params">{ data }</span>) =></span> { data.<span class="hljs-title function_">getReader</span>().<span class="hljs-title function_">read</span>().<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">chunk</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(chunk); }); }; port2.<span class="hljs-title function_">postMessage</span>(stream, [stream]);</code></pre> <h4>Class: <code>ReadableStreamDefaultReader</code><span><a class="mark" href="#class-readablestreamdefaultreader" id="class-readablestreamdefaultreader">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreamdefaultreader"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>By default, calling <code>readableStream.getReader()</code> with no arguments will return an instance of <code>ReadableStreamDefaultReader</code>. The default reader treats the chunks of data passed through the stream as opaque values, which allows the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to work with generally any JavaScript value.</p> <h5><code>new ReadableStreamDefaultReader(stream)</code><span><a class="mark" href="#new-readablestreamdefaultreaderstream" id="new-readablestreamdefaultreaderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestreamdefaultreader_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <p>Creates a new <a href="webstreams.html#class-readablestreamdefaultreader" class="type"><ReadableStreamDefaultReader></a> that is locked to the given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p> <h5><code>readableStreamDefaultReader.cancel([reason])</code><span><a class="mark" href="#readablestreamdefaultreadercancelreason" id="readablestreamdefaultreadercancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_cancel_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled when the underlying stream has been canceled.</p> <h5><code>readableStreamDefaultReader.closed</code><span><a class="mark" href="#readablestreamdefaultreaderclosed" id="readablestreamdefaultreaderclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_closed"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.</li> </ul> <h5><code>readableStreamDefaultReader.read()</code><span><a class="mark" href="#readablestreamdefaultreaderread" id="readablestreamdefaultreaderread">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_read"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Returns: A promise fulfilled with an object: <ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a></li> <li><code>done</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> </li> </ul> <p>Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled with the data once it is available.</p> <h5><code>readableStreamDefaultReader.releaseLock()</code><span><a class="mark" href="#readablestreamdefaultreaderreleaselock" id="readablestreamdefaultreaderreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultreader_releaselock"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p> <h4>Class: <code>ReadableStreamBYOBReader</code><span><a class="mark" href="#class-readablestreambyobreader" id="class-readablestreambyobreader">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreambyobreader"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>The <code>ReadableStreamBYOBReader</code> is an alternative consumer for byte-oriented <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>s (those that are created with <code>underlyingSource.type</code> set equal to <code>'bytes'</code> when the <code>ReadableStream</code> was created).</p> <p>The <code>BYOB</code> is short for "bring your own buffer". This is a pattern that allows for more efficient reading of byte-oriented data that avoids extraneous copying.</p> <pre><code class="language-js mjs"><span class="hljs-keyword">import</span> { open } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:fs/promises'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">ReadableStream</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>; <span class="hljs-keyword">class</span> <span class="hljs-title class_">Source</span> { type = <span class="hljs-string">'bytes'</span>; autoAllocateChunkSize = <span class="hljs-number">1024</span>; <span class="hljs-keyword">async</span> <span class="hljs-title function_">start</span>(<span class="hljs-params">controller</span>) { <span class="hljs-variable language_">this</span>.<span class="hljs-property">file</span> = <span class="hljs-keyword">await</span> <span class="hljs-title function_">open</span>(<span class="hljs-keyword">new</span> <span class="hljs-title function_">URL</span>(<span class="hljs-keyword">import</span>.<span class="hljs-property">meta</span>.<span class="hljs-property">url</span>)); <span class="hljs-variable language_">this</span>.<span class="hljs-property">controller</span> = controller; } <span class="hljs-keyword">async</span> <span class="hljs-title function_">pull</span>(<span class="hljs-params">controller</span>) { <span class="hljs-keyword">const</span> view = controller.<span class="hljs-property">byobRequest</span>?.<span class="hljs-property">view</span>; <span class="hljs-keyword">const</span> { bytesRead, } = <span class="hljs-keyword">await</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">file</span>.<span class="hljs-title function_">read</span>({ <span class="hljs-attr">buffer</span>: view, <span class="hljs-attr">offset</span>: view.<span class="hljs-property">byteOffset</span>, <span class="hljs-attr">length</span>: view.<span class="hljs-property">byteLength</span> }); <span class="hljs-keyword">if</span> (bytesRead === <span class="hljs-number">0</span>) { <span class="hljs-keyword">await</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">file</span>.<span class="hljs-title function_">close</span>(); <span class="hljs-variable language_">this</span>.<span class="hljs-property">controller</span>.<span class="hljs-title function_">close</span>(); } controller.<span class="hljs-property">byobRequest</span>.<span class="hljs-title function_">respond</span>(bytesRead); } } <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">ReadableStream</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Source</span>()); <span class="hljs-keyword">async</span> <span class="hljs-keyword">function</span> <span class="hljs-title function_">read</span>(<span class="hljs-params">stream</span>) { <span class="hljs-keyword">const</span> reader = stream.<span class="hljs-title function_">getReader</span>({ <span class="hljs-attr">mode</span>: <span class="hljs-string">'byob'</span> }); <span class="hljs-keyword">const</span> chunks = []; <span class="hljs-keyword">let</span> result; <span class="hljs-keyword">do</span> { result = <span class="hljs-keyword">await</span> reader.<span class="hljs-title function_">read</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">alloc</span>(<span class="hljs-number">100</span>)); <span class="hljs-keyword">if</span> (result.<span class="hljs-property">value</span> !== <span class="hljs-literal">undefined</span>) chunks.<span class="hljs-title function_">push</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(result.<span class="hljs-property">value</span>)); } <span class="hljs-keyword">while</span> (!result.<span class="hljs-property">done</span>); <span class="hljs-keyword">return</span> <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">concat</span>(chunks); } <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">read</span>(stream); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(data).<span class="hljs-title function_">toString</span>());</code></pre> <h5><code>new ReadableStreamBYOBReader(stream)</code><span><a class="mark" href="#new-readablestreambyobreaderstream" id="new-readablestreambyobreaderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_readablestreambyobreader_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <p>Creates a new <code>ReadableStreamBYOBReader</code> that is locked to the given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p> <h5><code>readableStreamBYOBReader.cancel([reason])</code><span><a class="mark" href="#readablestreambyobreadercancelreason" id="readablestreambyobreadercancelreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_cancel_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled when the underlying stream has been canceled.</p> <h5><code>readableStreamBYOBReader.closed</code><span><a class="mark" href="#readablestreambyobreaderclosed" id="readablestreambyobreaderclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_closed"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.</li> </ul> <h5><code>readableStreamBYOBReader.read(view)</code><span><a class="mark" href="#readablestreambyobreaderreadview" id="readablestreambyobreaderreadview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_read_view"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>view</code> <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a></li> <li>Returns: A promise fulfilled with an object: <ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a></li> <li><code>done</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> </li> </ul> <p>Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled with the data once it is available.</p> <p>Do not pass a pooled <a href="buffer.html#class-buffer" class="type"><Buffer></a> object instance in to this method. Pooled <code>Buffer</code> objects are created using <code>Buffer.allocUnsafe()</code>, or <code>Buffer.from()</code>, or are often returned by various <code>node:fs</code> module callbacks. These types of <code>Buffer</code>s use a shared underlying <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> object that contains all of the data from all of the pooled <code>Buffer</code> instances. When a <code>Buffer</code>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a>, or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> is passed in to <code>readableStreamBYOBReader.read()</code>, the view's underlying <code>ArrayBuffer</code> is <em>detached</em>, invalidating all existing views that may exist on that <code>ArrayBuffer</code>. This can have disastrous consequences for your application.</p> <h5><code>readableStreamBYOBReader.releaseLock()</code><span><a class="mark" href="#readablestreambyobreaderreleaselock" id="readablestreambyobreaderreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobreader_releaselock"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p> <h4>Class: <code>ReadableStreamDefaultController</code><span><a class="mark" href="#class-readablestreamdefaultcontroller" id="class-readablestreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreamdefaultcontroller"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for the internal state and management of the stream's queue. The <code>ReadableStreamDefaultController</code> is the default controller implementation for <code>ReadableStream</code>s that are not byte-oriented.</p> <h5><code>readableStreamDefaultController.close()</code><span><a class="mark" href="#readablestreamdefaultcontrollerclose" id="readablestreamdefaultcontrollerclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_close"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.</p> <h5><code>readableStreamDefaultController.desiredSize</code><span><a class="mark" href="#readablestreamdefaultcontrollerdesiredsize" id="readablestreamdefaultcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_desiredsize"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p> <h5><code>readableStreamDefaultController.enqueue(chunk)</code><span><a class="mark" href="#readablestreamdefaultcontrollerenqueuechunk" id="readablestreamdefaultcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_enqueue_chunk"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p> <h5><code>readableStreamDefaultController.error(error)</code><span><a class="mark" href="#readablestreamdefaultcontrollererrorerror" id="readablestreamdefaultcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreamdefaultcontroller_error_error"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.</p> <h4>Class: <code>ReadableByteStreamController</code><span><a class="mark" href="#class-readablebytestreamcontroller" id="class-readablebytestreamcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablebytestreamcontroller"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for the internal state and management of the stream's queue. The <code>ReadableByteStreamController</code> is for byte-oriented <code>ReadableStream</code>s.</p> <h5><code>readableByteStreamController.byobRequest</code><span><a class="mark" href="#readablebytestreamcontrollerbyobrequest" id="readablebytestreamcontrollerbyobrequest">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_byobrequest"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-readablestreambyobrequest" class="type"><ReadableStreamBYOBRequest></a></li> </ul> <h5><code>readableByteStreamController.close()</code><span><a class="mark" href="#readablebytestreamcontrollerclose" id="readablebytestreamcontrollerclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_close"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.</p> <h5><code>readableByteStreamController.desiredSize</code><span><a class="mark" href="#readablebytestreamcontrollerdesiredsize" id="readablebytestreamcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_desiredsize"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p> <h5><code>readableByteStreamController.enqueue(chunk)</code><span><a class="mark" href="#readablebytestreamcontrollerenqueuechunk" id="readablebytestreamcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_enqueue_chunk"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>chunk</code>: <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a></li> </ul> <p>Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.</p> <h5><code>readableByteStreamController.error(error)</code><span><a class="mark" href="#readablebytestreamcontrollererrorerror" id="readablebytestreamcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablebytestreamcontroller_error_error"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.</p> <h4>Class: <code>ReadableStreamBYOBRequest</code><span><a class="mark" href="#class-readablestreambyobrequest" id="class-readablestreambyobrequest">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_readablestreambyobrequest"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>When using <code>ReadableByteStreamController</code> in byte-oriented streams, and when using the <code>ReadableStreamBYOBReader</code>, the <code>readableByteStreamController.byobRequest</code> property provides access to a <code>ReadableStreamBYOBRequest</code> instance that represents the current read request. The object is used to gain access to the <code>ArrayBuffer</code>/<code>TypedArray</code> that has been provided for the read request to fill, and provides methods for signaling that the data has been provided.</p> <h5><code>readableStreamBYOBRequest.respond(bytesWritten)</code><span><a class="mark" href="#readablestreambyobrequestrespondbyteswritten" id="readablestreambyobrequestrespondbyteswritten">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_respond_byteswritten"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>bytesWritten</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>Signals that a <code>bytesWritten</code> number of bytes have been written to <code>readableStreamBYOBRequest.view</code>.</p> <h5><code>readableStreamBYOBRequest.respondWithNewView(view)</code><span><a class="mark" href="#readablestreambyobrequestrespondwithnewviewview" id="readablestreambyobrequestrespondwithnewviewview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_respondwithnewview_view"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>view</code> <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a></li> </ul> <p>Signals that the request has been fulfilled with bytes written to a new <code>Buffer</code>, <code>TypedArray</code>, or <code>DataView</code>.</p> <h5><code>readableStreamBYOBRequest.view</code><span><a class="mark" href="#readablestreambyobrequestview" id="readablestreambyobrequestview">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_readablestreambyobrequest_view"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a></li> </ul> <h4>Class: <code>WritableStream</code><span><a class="mark" href="#class-writablestream" id="class-writablestream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestream"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>The <code>WritableStream</code> is a destination to which stream data is sent.</p> <pre><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">WritableStream</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WritableStream</span>({ <span class="hljs-title function_">write</span>(<span class="hljs-params">chunk</span>) { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(chunk); } }); <span class="hljs-keyword">await</span> stream.<span class="hljs-title function_">getWriter</span>().<span class="hljs-title function_">write</span>(<span class="hljs-string">'Hello World'</span>);</code></pre> <h5><code>new WritableStream([underlyingSink[, strategy]])</code><span><a class="mark" href="#new-writablestreamunderlyingsink-strategy" id="new-writablestreamunderlyingsink-strategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_writablestream_underlyingsink_strategy"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>underlyingSink</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the <code>WritableStream</code> is created. <ul> <li><code>controller</code> <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a></li> <li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>write</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked when a chunk of data has been written to the <code>WritableStream</code>. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>controller</code> <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>close</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the <code>WritableStream</code> is closed. <ul> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>abort</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called to abruptly close the <code>WritableStream</code>. <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The <code>type</code> option is reserved for future use and <em>must</em> be undefined.</li> </ul> </li> <li><code>strategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.</li> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> </li> </ul> <h5><code>writableStream.abort([reason])</code><span><a class="mark" href="#writablestreamabortreason" id="writablestreamabortreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_abort_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Abruptly terminates the <code>WritableStream</code>. All queued writes will be canceled with their associated promises rejected.</p> <h5><code>writableStream.close()</code><span><a class="mark" href="#writablestreamclose" id="writablestreamclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_close"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Closes the <code>WritableStream</code> when no additional writes are expected.</p> <h5><code>writableStream.getWriter()</code><span><a class="mark" href="#writablestreamgetwriter" id="writablestreamgetwriter">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_getwriter"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Returns: <a href="webstreams.html#class-writablestreamdefaultwriter" class="type"><WritableStreamDefaultWriter></a></li> </ul> <p>Creates and creates a new writer instance that can be used to write data into the <code>WritableStream</code>.</p> <h5><code>writableStream.locked</code><span><a class="mark" href="#writablestreamlocked" id="writablestreamlocked">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestream_locked"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>The <code>writableStream.locked</code> property is <code>false</code> by default, and is switched to <code>true</code> while there is an active writer attached to this <code>WritableStream</code>.</p> <h5>Transferring with postMessage()<span><a class="mark" href="#transferring-with-postmessage_1" id="transferring-with-postmessage_1">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage_1"></a></h5> <p>A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">WritableStream</span>(<span class="hljs-title function_">getWritableSinkSomehow</span>()); <span class="hljs-keyword">const</span> { port1, port2 } = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MessageChannel</span>(); port1.<span class="hljs-property">onmessage</span> = <span class="hljs-function">(<span class="hljs-params">{ data }</span>) =></span> { data.<span class="hljs-title function_">getWriter</span>().<span class="hljs-title function_">write</span>(<span class="hljs-string">'hello'</span>); }; port2.<span class="hljs-title function_">postMessage</span>(stream, [stream]);</code></pre> <h4>Class: <code>WritableStreamDefaultWriter</code><span><a class="mark" href="#class-writablestreamdefaultwriter" id="class-writablestreamdefaultwriter">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestreamdefaultwriter"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <h5><code>new WritableStreamDefaultWriter(stream)</code><span><a class="mark" href="#new-writablestreamdefaultwriterstream" id="new-writablestreamdefaultwriterstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_writablestreamdefaultwriter_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li> </ul> <p>Creates a new <code>WritableStreamDefaultWriter</code> that is locked to the given <code>WritableStream</code>.</p> <h5><code>writableStreamDefaultWriter.abort([reason])</code><span><a class="mark" href="#writablestreamdefaultwriterabortreason" id="writablestreamdefaultwriterabortreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_abort_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Abruptly terminates the <code>WritableStream</code>. All queued writes will be canceled with their associated promises rejected.</p> <h5><code>writableStreamDefaultWriter.close()</code><span><a class="mark" href="#writablestreamdefaultwriterclose" id="writablestreamdefaultwriterclose">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_close"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Closes the <code>WritableStream</code> when no additional writes are expected.</p> <h5><code>writableStreamDefaultWriter.closed</code><span><a class="mark" href="#writablestreamdefaultwriterclosed" id="writablestreamdefaultwriterclosed">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_closed"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with <code>undefined</code> when the associated <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is closed or rejected if the stream errors or the writer's lock is released before the stream finishes closing.</li> </ul> <h5><code>writableStreamDefaultWriter.desiredSize</code><span><a class="mark" href="#writablestreamdefaultwriterdesiredsize" id="writablestreamdefaultwriterdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_desiredsize"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>The amount of data required to fill the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.</p> <h5><code>writableStreamDefaultWriter.ready</code><span><a class="mark" href="#writablestreamdefaultwriterready" id="writablestreamdefaultwriterready">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_ready"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>type: A promise that is fulfilled with <code>undefined</code> when the writer is ready to be used.</li> </ul> <h5><code>writableStreamDefaultWriter.releaseLock()</code><span><a class="mark" href="#writablestreamdefaultwriterreleaselock" id="writablestreamdefaultwriterreleaselock">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_releaselock"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Releases this writer's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.</p> <h5><code>writableStreamDefaultWriter.write([chunk])</code><span><a class="mark" href="#writablestreamdefaultwriterwritechunk" id="writablestreamdefaultwriterwritechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultwriter_write_chunk"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>chunk</code>: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> <p>Appends a new chunk of data to the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.</p> <h4>Class: <code>WritableStreamDefaultController</code><span><a class="mark" href="#class-writablestreamdefaultcontroller" id="class-writablestreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_writablestreamdefaultcontroller"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>The <code>WritableStreamDefaultController</code> manage's the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s internal state.</p> <h5><code>writableStreamDefaultController.abortReason</code><span><a class="mark" href="#writablestreamdefaultcontrollerabortreason" id="writablestreamdefaultcontrollerabortreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultcontroller_abortreason"></a></h5> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The <code>reason</code> value passed to <code>writableStream.abort()</code>.</li> </ul> <h5><code>writableStreamDefaultController.error(error)</code><span><a class="mark" href="#writablestreamdefaultcontrollererrorerror" id="writablestreamdefaultcontrollererrorerror">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultcontroller_error_error"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>error</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Called by user-code to signal that an error has occurred while processing the <code>WritableStream</code> data. When called, the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> will be aborted, with currently pending writes canceled.</p> <h5><code>writableStreamDefaultController.signal</code><span><a class="mark" href="#writablestreamdefaultcontrollersignal" id="writablestreamdefaultcontrollersignal">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_writablestreamdefaultcontroller_signal"></a></h5> <ul> <li>Type: <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> An <code>AbortSignal</code> that can be used to cancel pending write or close operations when a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is aborted.</li> </ul> <h4>Class: <code>TransformStream</code><span><a class="mark" href="#class-transformstream" id="class-transformstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_transformstream"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>A <code>TransformStream</code> consists of a <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> that are connected such that the data written to the <code>WritableStream</code> is received, and potentially transformed, before being pushed into the <code>ReadableStream</code>'s queue.</p> <pre><code class="language-js mjs"><span class="hljs-keyword">import</span> { <span class="hljs-title class_">TransformStream</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/web'</span>; <span class="hljs-keyword">const</span> transform = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TransformStream</span>({ <span class="hljs-title function_">transform</span>(<span class="hljs-params">chunk, controller</span>) { controller.<span class="hljs-title function_">enqueue</span>(chunk.<span class="hljs-title function_">toUpperCase</span>()); } }); <span class="hljs-keyword">await</span> <span class="hljs-title class_">Promise</span>.<span class="hljs-title function_">all</span>([ transform.<span class="hljs-property">writable</span>.<span class="hljs-title function_">getWriter</span>().<span class="hljs-title function_">write</span>(<span class="hljs-string">'A'</span>), transform.<span class="hljs-property">readable</span>.<span class="hljs-title function_">getReader</span>().<span class="hljs-title function_">read</span>(), ]);</code></pre> <h5><code>new TransformStream([transformer[, writableStrategy[, readableStrategy]]])</code><span><a class="mark" href="#new-transformstreamtransformer-writablestrategy-readablestrategy" id="new-transformstreamtransformer-writablestrategy-readablestrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_transformstream_transformer_writablestrategy_readablestrategy"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>transformer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the <code>TransformStream</code> is created. <ul> <li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li> <li>Returns: <code>undefined</code> or a promise fulfilled with <code>undefined</code></li> </ul> </li> <li><code>transform</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that receives, and potentially modifies, a chunk of data written to <code>transformStream.writable</code>, before forwarding that on to <code>transformStream.readable</code>. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>flush</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called immediately before the writable side of the <code>TransformStream</code> is closed, signaling the end of the transformation process. <ul> <li><code>controller</code> <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a></li> <li>Returns: A promise fulfilled with <code>undefined</code>.</li> </ul> </li> <li><code>readableType</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the <code>readableType</code> option is reserved for future use and <em>must</em> be <code>undefined</code>.</li> <li><code>writableType</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the <code>writableType</code> option is reserved for future use and <em>must</em> be <code>undefined</code>.</li> </ul> </li> <li><code>writableStrategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.</li> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> </li> <li><code>readableStrategy</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.</li> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data. <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> </li> </ul> <h5><code>transformStream.readable</code><span><a class="mark" href="#transformstreamreadable" id="transformstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstream_readable"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <h5><code>transformStream.writable</code><span><a class="mark" href="#transformstreamwritable" id="transformstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstream_writable"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li> </ul> <h5>Transferring with postMessage()<span><a class="mark" href="#transferring-with-postmessage_2" id="transferring-with-postmessage_2">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transferring_with_postmessage_2"></a></h5> <p>A <a href="webstreams.html#class-transformstream" class="type"><TransformStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.</p> <pre><code class="language-js"><span class="hljs-keyword">const</span> stream = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TransformStream</span>(); <span class="hljs-keyword">const</span> { port1, port2 } = <span class="hljs-keyword">new</span> <span class="hljs-title class_">MessageChannel</span>(); port1.<span class="hljs-property">onmessage</span> = <span class="hljs-function">(<span class="hljs-params">{ data }</span>) =></span> { <span class="hljs-keyword">const</span> { writable, readable } = data; <span class="hljs-comment">// ...</span> }; port2.<span class="hljs-title function_">postMessage</span>(stream, [stream]);</code></pre> <h4>Class: <code>TransformStreamDefaultController</code><span><a class="mark" href="#class-transformstreamdefaultcontroller" id="class-transformstreamdefaultcontroller">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_transformstreamdefaultcontroller"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>The <code>TransformStreamDefaultController</code> manages the internal state of the <code>TransformStream</code>.</p> <h5><code>transformStreamDefaultController.desiredSize</code><span><a class="mark" href="#transformstreamdefaultcontrollerdesiredsize" id="transformstreamdefaultcontrollerdesiredsize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_desiredsize"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>The amount of data required to fill the readable side's queue.</p> <h5><code>transformStreamDefaultController.enqueue([chunk])</code><span><a class="mark" href="#transformstreamdefaultcontrollerenqueuechunk" id="transformstreamdefaultcontrollerenqueuechunk">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_enqueue_chunk"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Appends a chunk of data to the readable side's queue.</p> <h5><code>transformStreamDefaultController.error([reason])</code><span><a class="mark" href="#transformstreamdefaultcontrollererrorreason" id="transformstreamdefaultcontrollererrorreason">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_error_reason"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>reason</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> </ul> <p>Signals to both the readable and writable side that an error has occurred while processing the transform data, causing both sides to be abruptly closed.</p> <h5><code>transformStreamDefaultController.terminate()</code><span><a class="mark" href="#transformstreamdefaultcontrollerterminate" id="transformstreamdefaultcontrollerterminate">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_transformstreamdefaultcontroller_terminate"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <p>Closes the readable side of the transport and causes the writable side to be abruptly closed with an error.</p> <h4>Class: <code>ByteLengthQueuingStrategy</code><span><a class="mark" href="#class-bytelengthqueuingstrategy" id="class-bytelengthqueuingstrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_bytelengthqueuingstrategy"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <h5><code>new ByteLengthQueuingStrategy(options)</code><span><a class="mark" href="#new-bytelengthqueuingstrategyoptions" id="new-bytelengthqueuingstrategyoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_bytelengthqueuingstrategy_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> <h5><code>byteLengthQueuingStrategy.highWaterMark</code><span><a class="mark" href="#bytelengthqueuingstrategyhighwatermark" id="bytelengthqueuingstrategyhighwatermark">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_bytelengthqueuingstrategy_highwatermark"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <h5><code>byteLengthQueuingStrategy.size</code><span><a class="mark" href="#bytelengthqueuingstrategysize" id="bytelengthqueuingstrategysize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_bytelengthqueuingstrategy_size"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> <h4>Class: <code>CountQueuingStrategy</code><span><a class="mark" href="#class-countqueuingstrategy" id="class-countqueuingstrategy">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_countqueuingstrategy"></a></h4> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <h5><code>new CountQueuingStrategy(options)</code><span><a class="mark" href="#new-countqueuingstrategyoptions" id="new-countqueuingstrategyoptions">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_countqueuingstrategy_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>highWaterMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> <h5><code>countQueuingStrategy.highWaterMark</code><span><a class="mark" href="#countqueuingstrategyhighwatermark" id="countqueuingstrategyhighwatermark">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_countqueuingstrategy_highwatermark"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <h5><code>countQueuingStrategy.size</code><span><a class="mark" href="#countqueuingstrategysize" id="countqueuingstrategysize">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_countqueuingstrategy_size"></a></h5> <div class="api_metadata"> <span>Added in: v16.5.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> <ul> <li><code>chunk</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> </li> </ul> <h4>Class: <code>TextEncoderStream</code><span><a class="mark" href="#class-textencoderstream" id="class-textencoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_textencoderstream"></a></h4> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <h5><code>new TextEncoderStream()</code><span><a class="mark" href="#new-textencoderstream" id="new-textencoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_textencoderstream"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <p>Creates a new <code>TextEncoderStream</code> instance.</p> <h5><code>textEncoderStream.encoding</code><span><a class="mark" href="#textencoderstreamencoding" id="textencoderstreamencoding">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_encoding"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>The encoding supported by the <code>TextEncoderStream</code> instance.</p> <h5><code>textEncoderStream.readable</code><span><a class="mark" href="#textencoderstreamreadable" id="textencoderstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_readable"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <h5><code>textEncoderStream.writable</code><span><a class="mark" href="#textencoderstreamwritable" id="textencoderstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textencoderstream_writable"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li> </ul> <h4>Class: <code>TextDecoderStream</code><span><a class="mark" href="#class-textdecoderstream" id="class-textdecoderstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_class_textdecoderstream"></a></h4> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <h5><code>new TextDecoderStream([encoding[, options]])</code><span><a class="mark" href="#new-textdecoderstreamencoding-options" id="new-textdecoderstreamencoding-options">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_new_textdecoderstream_encoding_options"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Identifies the <code>encoding</code> that this <code>TextDecoder</code> instance supports. <strong>Default:</strong> <code>'utf-8'</code>.</li> <li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <ul> <li><code>fatal</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if decoding failures are fatal.</li> <li><code>ignoreBOM</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> When <code>true</code>, the <code>TextDecoderStream</code> will include the byte order mark in the decoded result. When <code>false</code>, the byte order mark will be removed from the output. This option is only used when <code>encoding</code> is <code>'utf-8'</code>, <code>'utf-16be'</code>, or <code>'utf-16le'</code>. <strong>Default:</strong> <code>false</code>.</li> </ul> </li> </ul> <p>Creates a new <code>TextDecoderStream</code> instance.</p> <h5><code>textDecoderStream.encoding</code><span><a class="mark" href="#textdecoderstreamencoding" id="textdecoderstreamencoding">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_encoding"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>The encoding supported by the <code>TextDecoderStream</code> instance.</p> <h5><code>textDecoderStream.fatal</code><span><a class="mark" href="#textdecoderstreamfatal" id="textdecoderstreamfatal">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_fatal"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>The value will be <code>true</code> if decoding errors result in a <code>TypeError</code> being thrown.</p> <h5><code>textDecoderStream.ignoreBOM</code><span><a class="mark" href="#textdecoderstreamignorebom" id="textdecoderstreamignorebom">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_ignorebom"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>The value will be <code>true</code> if the decoding result will include the byte order mark.</p> <h5><code>textDecoderStream.readable</code><span><a class="mark" href="#textdecoderstreamreadable" id="textdecoderstreamreadable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_readable"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a></li> </ul> <h5><code>textDecoderStream.writable</code><span><a class="mark" href="#textdecoderstreamwritable" id="textdecoderstreamwritable">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_textdecoderstream_writable"></a></h5> <div class="api_metadata"> <span>Added in: v16.6.0</span> </div> <ul> <li>Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a></li> </ul> <h4>Utility Consumers<span><a class="mark" href="#utility-consumers" id="utility-consumers">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_utility_consumers"></a></h4> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <p>The utility consumer functions provide common options for consuming streams.</p> <p>They are accessed using:</p> <pre class="with-14-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { arrayBuffer, blob, buffer, json, text, } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>;</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { arrayBuffer, blob, buffer, json, text, } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>);</code></pre> <h5><code>streamConsumers.arrayBuffer(stream)</code><span><a class="mark" href="#streamconsumersarraybufferstream" id="streamconsumersarraybufferstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_arraybuffer_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with an <code>ArrayBuffer</code> containing the full contents of the stream.</li> </ul> <pre class="with-62-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { buffer <span class="hljs-keyword">as</span> arrayBuffer } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Readable</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">TextEncoder</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:util'</span>; <span class="hljs-keyword">const</span> encoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TextEncoder</span>(); <span class="hljs-keyword">const</span> dataArray = encoder.<span class="hljs-title function_">encode</span>(<span class="hljs-string">'hello world from consumers!'</span>); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(dataArray); <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">arrayBuffer</span>(readable); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.byteLength}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { arrayBuffer } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">Readable</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'stream'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">TextEncoder</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'util'</span>); <span class="hljs-keyword">const</span> encoder = <span class="hljs-keyword">new</span> <span class="hljs-title class_">TextEncoder</span>(); <span class="hljs-keyword">const</span> dataArray = encoder.<span class="hljs-title function_">encode</span>([<span class="hljs-string">'hello world from consumers!'</span>]); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(dataArray); <span class="hljs-title function_">arrayBuffer</span>(readable).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.byteLength}</span>`</span>); });</code></pre> <h5><code>streamConsumers.blob(stream)</code><span><a class="mark" href="#streamconsumersblobstream" id="streamconsumersblobstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_blob_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-blob" class="type"><Blob></a> containing the full contents of the stream.</li> </ul> <pre class="with-50-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { blob } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>; <span class="hljs-keyword">const</span> dataBlob = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Blob</span>([<span class="hljs-string">'hello world from consumers!'</span>]); <span class="hljs-keyword">const</span> readable = dataBlob.<span class="hljs-title function_">stream</span>(); <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">blob</span>(readable); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.size}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { blob } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>); <span class="hljs-keyword">const</span> dataBlob = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Blob</span>([<span class="hljs-string">'hello world from consumers!'</span>]); <span class="hljs-keyword">const</span> readable = dataBlob.<span class="hljs-title function_">stream</span>(); <span class="hljs-title function_">blob</span>(readable).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.size}</span>`</span>); });</code></pre> <h5><code>streamConsumers.buffer(stream)</code><span><a class="mark" href="#streamconsumersbufferstream" id="streamconsumersbufferstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_buffer_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-buffer" class="type"><Buffer></a> containing the full contents of the stream.</li> </ul> <pre class="with-52-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { buffer } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Readable</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Buffer</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:buffer'</span>; <span class="hljs-keyword">const</span> dataBuffer = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'hello world from consumers!'</span>); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(dataBuffer); <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">buffer</span>(readable); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { buffer } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">Readable</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">Buffer</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:buffer'</span>); <span class="hljs-keyword">const</span> dataBuffer = <span class="hljs-title class_">Buffer</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'hello world from consumers!'</span>); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(dataBuffer); <span class="hljs-title function_">buffer</span>(readable).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>); });</code></pre> <h5><code>streamConsumers.json(stream)</code><span><a class="mark" href="#streamconsumersjsonstream" id="streamconsumersjsonstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_json_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a UTF-8 encoded string that is then passed through <code>JSON.parse()</code>.</li> </ul> <pre class="with-50-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { json } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Readable</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream'</span>; <span class="hljs-keyword">const</span> items = <span class="hljs-title class_">Array</span>.<span class="hljs-title function_">from</span>( { <span class="hljs-attr">length</span>: <span class="hljs-number">100</span> }, <span class="hljs-function">() =></span> ({ <span class="hljs-attr">message</span>: <span class="hljs-string">'hello world from consumers!'</span> }) ); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(<span class="hljs-title class_">JSON</span>.<span class="hljs-title function_">stringify</span>(items)); <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">json</span>(readable); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { json } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">Readable</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream'</span>); <span class="hljs-keyword">const</span> items = <span class="hljs-title class_">Array</span>.<span class="hljs-title function_">from</span>( { <span class="hljs-attr">length</span>: <span class="hljs-number">100</span> }, <span class="hljs-function">() =></span> ({ <span class="hljs-attr">message</span>: <span class="hljs-string">'hello world from consumers!'</span> }) ); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(<span class="hljs-title class_">JSON</span>.<span class="hljs-title function_">stringify</span>(items)); <span class="hljs-title function_">json</span>(readable).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>); });</code></pre> <h5><code>streamConsumers.text(stream)</code><span><a class="mark" href="#streamconsumerstextstream" id="streamconsumerstextstream">#</a></span><a aria-hidden="true" class="legacy" id="webstreams_streamconsumers_text_stream"></a></h5> <div class="api_metadata"> <span>Added in: v16.7.0</span> </div> <ul> <li><code>stream</code> <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a UTF-8 encoded string.</li> </ul> <pre class="with-65-chars"><input class="js-flavor-selector" type="checkbox" checked aria-label="Show modern ES modules syntax"><code class="language-js mjs"><span class="hljs-keyword">import</span> { json, text, blob, buffer } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream/consumers'</span>; <span class="hljs-keyword">import</span> { <span class="hljs-title class_">Readable</span> } <span class="hljs-keyword">from</span> <span class="hljs-string">'node:stream'</span>; <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'Hello world from consumers!'</span>); <span class="hljs-keyword">const</span> data = <span class="hljs-keyword">await</span> <span class="hljs-title function_">text</span>(readable); <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>);</code><code class="language-js cjs"><span class="hljs-keyword">const</span> { text } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream/consumers'</span>); <span class="hljs-keyword">const</span> { <span class="hljs-title class_">Readable</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:stream'</span>); <span class="hljs-keyword">const</span> readable = <span class="hljs-title class_">Readable</span>.<span class="hljs-title function_">from</span>(<span class="hljs-string">'Hello world from consumers!'</span>); <span class="hljs-title function_">text</span>(readable).<span class="hljs-title function_">then</span>(<span class="hljs-function">(<span class="hljs-params">data</span>) =></span> { <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`from readable: <span class="hljs-subst">${data.length}</span>`</span>); });</code></pre></section> <!-- API END --> </div> </div> </div> </body> </html>