learnyounode

<!DOCTYPE html><html lang="en"><head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <title>Stream | Node.js v12.10.0 Documentation</title> <link rel="stylesheet" href="data:text/css;base64,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"> <link rel="stylesheet" href="data:text/css;base64,/*--------------------- Layout and Typography ----------------------------*/
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.changelog > summary {
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.github_icon {
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"> <link rel="stylesheet" href="data:text/css;base64,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"> <link rel="canonical" href="https://nodejs.org/api/stream.html"> </head> <body class="alt apidoc" id="api-section-stream"> <div id="content" class="clearfix"> <div id="column2" class="interior"> <div id="intro" class="interior"> <a href="https://nodejs.org/" title="Go back to the home page"> Node.js </a> </div> <ul> <li><a href="https://nodejs.org/api/documentation.html" class="nav-documentation">About these Docs</a></li> <li><a href="https://nodejs.org/api/synopsis.html" class="nav-synopsis">Usage & Example</a></li> </ul> <div class="line"></div> <ul> <li><a href="https://nodejs.org/api/assert.html" class="nav-assert">Assertion Testing</a></li> <li><a href="https://nodejs.org/api/async_hooks.html" class="nav-async_hooks">Async Hooks</a></li> <li><a href="https://nodejs.org/api/buffer.html" class="nav-buffer">Buffer</a></li> <li><a href="https://nodejs.org/api/addons.html" class="nav-addons">C++ Addons</a></li> <li><a href="https://nodejs.org/api/n-api.html" class="nav-n-api">C/C++ Addons - N-API</a></li> <li><a href="https://nodejs.org/api/child_process.html" class="nav-child_process">Child Processes</a></li> <li><a href="https://nodejs.org/api/cluster.html" class="nav-cluster">Cluster</a></li> <li><a href="https://nodejs.org/api/cli.html" class="nav-cli">Command Line Options</a></li> <li><a href="https://nodejs.org/api/console.html" class="nav-console">Console</a></li> <li><a href="https://nodejs.org/api/crypto.html" class="nav-crypto">Crypto</a></li> <li><a href="https://nodejs.org/api/debugger.html" class="nav-debugger">Debugger</a></li> <li><a href="https://nodejs.org/api/deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> <li><a href="https://nodejs.org/api/dns.html" class="nav-dns">DNS</a></li> <li><a href="https://nodejs.org/api/domain.html" class="nav-domain">Domain</a></li> <li><a href="https://nodejs.org/api/esm.html" class="nav-esm">ECMAScript Modules</a></li> <li><a href="https://nodejs.org/api/errors.html" class="nav-errors">Errors</a></li> <li><a href="https://nodejs.org/api/events.html" class="nav-events">Events</a></li> <li><a href="https://nodejs.org/api/fs.html" class="nav-fs">File System</a></li> <li><a href="https://nodejs.org/api/globals.html" class="nav-globals">Globals</a></li> <li><a href="https://nodejs.org/api/http.html" class="nav-http">HTTP</a></li> <li><a href="https://nodejs.org/api/http2.html" class="nav-http2">HTTP/2</a></li> <li><a href="https://nodejs.org/api/https.html" class="nav-https">HTTPS</a></li> <li><a href="https://nodejs.org/api/inspector.html" class="nav-inspector">Inspector</a></li> <li><a href="https://nodejs.org/api/intl.html" class="nav-intl">Internationalization</a></li> <li><a href="https://nodejs.org/api/modules.html" class="nav-modules">Modules</a></li> <li><a href="https://nodejs.org/api/net.html" class="nav-net">Net</a></li> <li><a href="https://nodejs.org/api/os.html" class="nav-os">OS</a></li> <li><a href="https://nodejs.org/api/path.html" class="nav-path">Path</a></li> <li><a href="https://nodejs.org/api/perf_hooks.html" class="nav-perf_hooks">Performance Hooks</a></li> <li><a href="https://nodejs.org/api/policy.html" class="nav-policy">Policies</a></li> <li><a href="https://nodejs.org/api/process.html" class="nav-process">Process</a></li> <li><a href="https://nodejs.org/api/punycode.html" class="nav-punycode">Punycode</a></li> <li><a href="https://nodejs.org/api/querystring.html" class="nav-querystring">Query Strings</a></li> <li><a href="https://nodejs.org/api/readline.html" class="nav-readline">Readline</a></li> <li><a href="https://nodejs.org/api/repl.html" class="nav-repl">REPL</a></li> <li><a href="https://nodejs.org/api/report.html" class="nav-report">Report</a></li> <li><a href="https://nodejs.org/api/stream.html" class="nav-stream active">Stream</a></li> <li><a href="https://nodejs.org/api/string_decoder.html" class="nav-string_decoder">String Decoder</a></li> <li><a href="https://nodejs.org/api/timers.html" class="nav-timers">Timers</a></li> <li><a href="https://nodejs.org/api/tls.html" class="nav-tls">TLS/SSL</a></li> <li><a href="https://nodejs.org/api/tracing.html" class="nav-tracing">Trace Events</a></li> <li><a href="https://nodejs.org/api/tty.html" class="nav-tty">TTY</a></li> <li><a href="https://nodejs.org/api/dgram.html" class="nav-dgram">UDP/Datagram</a></li> <li><a href="https://nodejs.org/api/url.html" class="nav-url">URL</a></li> <li><a href="https://nodejs.org/api/util.html" class="nav-util">Utilities</a></li> <li><a href="https://nodejs.org/api/v8.html" class="nav-v8">V8</a></li> <li><a href="https://nodejs.org/api/vm.html" class="nav-vm">VM</a></li> <li><a href="https://nodejs.org/api/worker_threads.html" class="nav-worker_threads">Worker Threads</a></li> <li><a href="https://nodejs.org/api/zlib.html" class="nav-zlib">Zlib</a></li> </ul> <div class="line"></div> <ul> <li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">GitHub Repo & Issue Tracker</a></li> </ul> </div> <div id="column1" data-id="stream" class="interior"> <header> <h1>Node.js v12.10.0 Documentation</h1> <div id="gtoc"> <ul> <li> <a href="https://nodejs.org/api/index.html" name="toc">Index</a> </li> <li> <a href="https://nodejs.org/api/all.html">View on single page</a> </li> <li> <a href="https://nodejs.org/api/stream.json">View as JSON</a> </li> <li class="version-picker"> <a href="#">View another version <span>▼</span></a> <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v12.x/api/stream.html">12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v11.x/api/stream.html">11.x</a></li> <li><a href="https://nodejs.org/docs/latest-v10.x/api/stream.html">10.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v9.x/api/stream.html">9.x</a></li> <li><a href="https://nodejs.org/docs/latest-v8.x/api/stream.html">8.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v7.x/api/stream.html">7.x</a></li> <li><a href="https://nodejs.org/docs/latest-v6.x/api/stream.html">6.x</a></li> <li><a href="https://nodejs.org/docs/latest-v5.x/api/stream.html">5.x</a></li> <li><a href="https://nodejs.org/docs/latest-v4.x/api/stream.html">4.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.12.x/api/stream.html">0.12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.10.x/api/stream.html">0.10.x</a></li></ol> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/stream.md"><span class="github_icon"><svg height="16" width="16" viewBox="0 0 16.1 16.1" fill="currentColor"><path d="M8 0a8 8 0 0 0-2.5 15.6c.4 0 .5-.2.5-.4v-1.5c-2 .4-2.5-.5-2.7-1 0-.1-.5-.9-.8-1-.3-.2-.7-.6 0-.6.6 0 1 .6 1.2.8.7 1.2 1.9 1 2.4.7 0-.5.2-.9.5-1-1.8-.3-3.7-1-3.7-4 0-.9.3-1.6.8-2.2 0-.2-.3-1 .1-2 0 0 .7-.3 2.2.7a7.4 7.4 0 0 1 4 0c1.5-1 2.2-.8 2.2-.8.5 1.1.2 2 .1 2.1.5.6.8 1.3.8 2.2 0 3-1.9 3.7-3.6 4 .3.2.5.7.5 1.4v2.2c0 .2.1.5.5.4A8 8 0 0 0 16 8a8 8 0 0 0-8-8z"></path></svg></span>Edit on GitHub</a></li> </ul> </div> <hr> </header> <div id="toc"> <h2>Table of Contents</h2> <ul> <li> <p><span class="stability_2"><a href="#stream_stream">Stream</a></span></p> <ul> <li><a href="#stream_organization_of_this_document">Organization of this Document</a></li> <li> <p><a href="#stream_types_of_streams">Types of Streams</a></p> <ul> <li><a href="#stream_object_mode">Object Mode</a></li> <li><a href="#stream_buffering">Buffering</a></li> </ul> </li> <li> <p><a href="#stream_api_for_stream_consumers">API for Stream Consumers</a></p> <ul> <li> <p><a href="#stream_writable_streams">Writable Streams</a></p> <ul> <li> <p><a href="#stream_class_stream_writable">Class: stream.Writable</a></p> <ul> <li><a href="#stream_event_close">Event: 'close'</a></li> <li><a href="#stream_event_drain">Event: 'drain'</a></li> <li><a href="#stream_event_error">Event: 'error'</a></li> <li><a href="#stream_event_finish">Event: 'finish'</a></li> <li><a href="#stream_event_pipe">Event: 'pipe'</a></li> <li><a href="#stream_event_unpipe">Event: 'unpipe'</a></li> <li><a href="#stream_writable_cork">writable.cork()</a></li> <li><a href="#stream_writable_destroy_error">writable.destroy([error])</a></li> <li><a href="#stream_writable_destroyed">writable.destroyed</a></li> <li><a href="#stream_writable_end_chunk_encoding_callback">writable.end([chunk][, encoding][, callback])</a></li> <li><a href="#stream_writable_setdefaultencoding_encoding">writable.setDefaultEncoding(encoding)</a></li> <li><a href="#stream_writable_uncork">writable.uncork()</a></li> <li><a href="#stream_writable_writable">writable.writable</a></li> <li><a href="#stream_writable_writableended">writable.writableEnded</a></li> <li><a href="#stream_writable_writablefinished">writable.writableFinished</a></li> <li><a href="#stream_writable_writablehighwatermark">writable.writableHighWaterMark</a></li> <li><a href="#stream_writable_writablelength">writable.writableLength</a></li> <li><a href="#stream_writable_writableobjectmode">writable.writableObjectMode</a></li> <li><a href="#stream_writable_write_chunk_encoding_callback">writable.write(chunk[, encoding][, callback])</a></li> </ul> </li> </ul> </li> <li> <p><a href="#stream_readable_streams">Readable Streams</a></p> <ul> <li><a href="#stream_two_reading_modes">Two Reading Modes</a></li> <li><a href="#stream_three_states">Three States</a></li> <li><a href="#stream_choose_one_api_style">Choose One API Style</a></li> <li> <p><a href="#stream_class_stream_readable">Class: stream.Readable</a></p> <ul> <li><a href="#stream_event_close_1">Event: 'close'</a></li> <li><a href="#stream_event_data">Event: 'data'</a></li> <li><a href="#stream_event_end">Event: 'end'</a></li> <li><a href="#stream_event_error_1">Event: 'error'</a></li> <li><a href="#stream_event_pause">Event: 'pause'</a></li> <li><a href="#stream_event_readable">Event: 'readable'</a></li> <li><a href="#stream_event_resume">Event: 'resume'</a></li> <li><a href="#stream_readable_destroy_error">readable.destroy([error])</a></li> <li><a href="#stream_readable_destroyed">readable.destroyed</a></li> <li><a href="#stream_readable_ispaused">readable.isPaused()</a></li> <li><a href="#stream_readable_pause">readable.pause()</a></li> <li><a href="#stream_readable_pipe_destination_options">readable.pipe(destination[, options])</a></li> <li><a href="#stream_readable_read_size">readable.read([size])</a></li> <li><a href="#stream_readable_readable">readable.readable</a></li> <li><a href="#stream_readable_readableencoding">readable.readableEncoding</a></li> <li><a href="#stream_readable_readableended">readable.readableEnded</a></li> <li><a href="#stream_readable_readablehighwatermark">readable.readableHighWaterMark</a></li> <li><a href="#stream_readable_readablelength">readable.readableLength</a></li> <li><a href="#stream_readable_readableobjectmode">readable.readableObjectMode</a></li> <li><a href="#stream_readable_resume">readable.resume()</a></li> <li><a href="#stream_readable_setencoding_encoding">readable.setEncoding(encoding)</a></li> <li><a href="#stream_readable_unpipe_destination">readable.unpipe([destination])</a></li> <li><a href="#stream_readable_unshift_chunk_encoding">readable.unshift(chunk[, encoding])</a></li> <li><a href="#stream_readable_wrap_stream">readable.wrap(stream)</a></li> <li><a href="#stream_readable_symbol_asynciterator">readable[Symbol.asyncIterator]()</a></li> </ul> </li> </ul> </li> <li> <p><a href="#stream_duplex_and_transform_streams">Duplex and Transform Streams</a></p> <ul> <li><a href="#stream_class_stream_duplex">Class: stream.Duplex</a></li> <li> <p><a href="#stream_class_stream_transform">Class: stream.Transform</a></p> <ul> <li><a href="#stream_transform_destroy_error">transform.destroy([error])</a></li> </ul> </li> </ul> </li> <li><a href="#stream_stream_finished_stream_options_callback">stream.finished(stream[, options], callback)</a></li> <li><a href="#stream_stream_pipeline_streams_callback">stream.pipeline(...streams, callback)</a></li> <li><a href="#stream_stream_readable_from_iterable_options">stream.Readable.from(iterable, [options])</a></li> </ul> </li> <li> <p><a href="#stream_api_for_stream_implementers">API for Stream Implementers</a></p> <ul> <li><a href="#stream_simplified_construction">Simplified Construction</a></li> <li> <p><a href="#stream_implementing_a_writable_stream">Implementing a Writable Stream</a></p> <ul> <li><a href="#stream_constructor_new_stream_writable_options">Constructor: new stream.Writable([options])</a></li> <li><a href="#stream_writable_write_chunk_encoding_callback_1">writable._write(chunk, encoding, callback)</a></li> <li><a href="#stream_writable_writev_chunks_callback">writable._writev(chunks, callback)</a></li> <li><a href="#stream_writable_destroy_err_callback">writable._destroy(err, callback)</a></li> <li><a href="#stream_writable_final_callback">writable._final(callback)</a></li> <li><a href="#stream_errors_while_writing">Errors While Writing</a></li> <li><a href="#stream_an_example_writable_stream">An Example Writable Stream</a></li> <li><a href="#stream_decoding_buffers_in_a_writable_stream">Decoding buffers in a Writable Stream</a></li> </ul> </li> <li> <p><a href="#stream_implementing_a_readable_stream">Implementing a Readable Stream</a></p> <ul> <li><a href="#stream_new_stream_readable_options">new stream.Readable([options])</a></li> <li><a href="#stream_readable_read_size_1">readable._read(size)</a></li> <li><a href="#stream_readable_destroy_err_callback">readable._destroy(err, callback)</a></li> <li><a href="#stream_readable_push_chunk_encoding">readable.push(chunk[, encoding])</a></li> <li><a href="#stream_errors_while_reading">Errors While Reading</a></li> <li><a href="#stream_an_example_counting_stream">An Example Counting Stream</a></li> </ul> </li> <li> <p><a href="#stream_implementing_a_duplex_stream">Implementing a Duplex Stream</a></p> <ul> <li><a href="#stream_new_stream_duplex_options">new stream.Duplex(options)</a></li> <li><a href="#stream_an_example_duplex_stream">An Example Duplex Stream</a></li> <li><a href="#stream_object_mode_duplex_streams">Object Mode Duplex Streams</a></li> </ul> </li> <li> <p><a href="#stream_implementing_a_transform_stream">Implementing a Transform Stream</a></p> <ul> <li><a href="#stream_new_stream_transform_options">new stream.Transform([options])</a></li> <li><a href="#stream_events_finish_and_end">Events: 'finish' and 'end'</a></li> <li><a href="#stream_transform_flush_callback">transform._flush(callback)</a></li> <li><a href="#stream_transform_transform_chunk_encoding_callback">transform._transform(chunk, encoding, callback)</a></li> <li><a href="#stream_class_stream_passthrough">Class: stream.PassThrough</a></li> </ul> </li> </ul> </li> <li> <p><a href="#stream_additional_notes">Additional Notes</a></p> <ul> <li> <p><a href="#stream_streams_compatibility_with_async_generators_and_async_iterators">Streams Compatibility with Async Generators and Async Iterators</a></p> <ul> <li><a href="#stream_consuming_readable_streams_with_async_iterators">Consuming Readable Streams with Async Iterators</a></li> <li><a href="#stream_creating_readable_streams_with_async_generators">Creating Readable Streams with Async Generators</a></li> <li><a href="#stream_piping_to_writable_streams_from_async_iterators">Piping to Writable Streams from Async Iterators</a></li> </ul> </li> <li><a href="#stream_compatibility_with_older_node_js_versions">Compatibility with Older Node.js Versions</a></li> <li><a href="#stream_readable_read_0"><code>readable.read(0)</code></a></li> <li><a href="#stream_readable_push"><code>readable.push('')</code></a></li> <li><a href="#stream_highwatermark_discrepancy_after_calling_readable_setencoding"><code>highWaterMark</code> discrepancy after calling <code>readable.setEncoding()</code></a></li> </ul> </li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Stream<a class="srclink" href="https://github.com/nodejs/node/blob/3a2e75d9a5c31d20e429d505b82dd182e33f459a/lib/stream.js#L32">[src]</a><span><a class="mark" href="#stream_stream" id="stream_stream">#</a></span></h1> <p></p><div class="api_stability api_stability_2"><a href="https://nodejs.org/api/documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p></p> <p>A stream is an abstract interface for working with streaming data in Node.js. The <code>stream</code> module provides an API for implementing the stream interface.</p> <p>There are many stream objects provided by Node.js. For instance, a <a href="https://nodejs.org/api/http.html#http_class_http_incomingmessage">request to an HTTP server</a> and <a href="https://nodejs.org/api/process.html#process_process_stdout"><code>process.stdout</code></a> are both stream instances.</p> <p>Streams can be readable, writable, or both. All streams are instances of <a href="https://nodejs.org/api/events.html#events_class_eventemitter"><code>EventEmitter</code></a>.</p> <p>To access the <code>stream</code> module:</p> <pre><code class="language-js">const stream = require('stream'); </code></pre> <p>The <code>stream</code> module is useful for creating new types of stream instances. It is usually not necessary to use the <code>stream</code> module to consume streams.</p> <h2>Organization of this Document<span><a class="mark" href="#stream_organization_of_this_document" id="stream_organization_of_this_document">#</a></span></h2> <p>This document contains two primary sections and a third section for notes. The first section explains how to use existing streams within an application. The second section explains how to create new types of streams.</p> <h2>Types of Streams<span><a class="mark" href="#stream_types_of_streams" id="stream_types_of_streams">#</a></span></h2> <p>There are four fundamental stream types within Node.js:</p> <ul> <li><a href="#stream_class_stream_writable"><code>Writable</code></a> - streams to which data can be written (for example, <a href="https://nodejs.org/api/fs.html#fs_fs_createwritestream_path_options"><code>fs.createWriteStream()</code></a>).</li> <li><a href="#stream_class_stream_readable"><code>Readable</code></a> - streams from which data can be read (for example, <a href="https://nodejs.org/api/fs.html#fs_fs_createreadstream_path_options"><code>fs.createReadStream()</code></a>).</li> <li><a href="#stream_class_stream_duplex"><code>Duplex</code></a> - streams that are both <code>Readable</code> and <code>Writable</code> (for example, <a href="https://nodejs.org/api/net.html#net_class_net_socket"><code>net.Socket</code></a>).</li> <li><a href="#stream_class_stream_transform"><code>Transform</code></a> - <code>Duplex</code> streams that can modify or transform the data as it is written and read (for example, <a href="https://nodejs.org/api/zlib.html#zlib_zlib_createdeflate_options"><code>zlib.createDeflate()</code></a>).</li> </ul> <p>Additionally, this module includes the utility functions <a href="#stream_stream_pipeline_streams_callback"><code>stream.pipeline()</code></a>, <a href="#stream_stream_finished_stream_options_callback"><code>stream.finished()</code></a> and <a href="#stream_stream_readable_from_iterable_options"><code>stream.Readable.from()</code></a>.</p> <h3>Object Mode<span><a class="mark" href="#stream_object_mode" id="stream_object_mode">#</a></span></h3> <p>All streams created by Node.js APIs operate exclusively on strings and <code>Buffer</code> (or <code>Uint8Array</code>) objects. It is possible, however, for stream implementations to work with other types of JavaScript values (with the exception of <code>null</code>, which serves a special purpose within streams). Such streams are considered to operate in "object mode".</p> <p>Stream instances are switched into object mode using the <code>objectMode</code> option when the stream is created. Attempting to switch an existing stream into object mode is not safe.</p> <h3>Buffering<span><a class="mark" href="#stream_buffering" id="stream_buffering">#</a></span></h3> <p>Both <a href="#stream_class_stream_writable"><code>Writable</code></a> and <a href="#stream_class_stream_readable"><code>Readable</code></a> streams will store data in an internal buffer that can be retrieved using <code>writable.writableBuffer</code> or <code>readable.readableBuffer</code>, respectively.</p> <p>The amount of data potentially buffered depends on the <code>highWaterMark</code> option passed into the stream's constructor. For normal streams, the <code>highWaterMark</code> option specifies a <a href="#stream_highwatermark_discrepancy_after_calling_readable_setencoding">total number of bytes</a>. For streams operating in object mode, the <code>highWaterMark</code> specifies a total number of objects.</p> <p>Data is buffered in <code>Readable</code> streams when the implementation calls <a href="#stream_readable_push_chunk_encoding"><code>stream.push(chunk)</code></a>. If the consumer of the Stream does not call <a href="#stream_readable_read_size"><code>stream.read()</code></a>, the data will sit in the internal queue until it is consumed.</p> <p>Once the total size of the internal read buffer reaches the threshold specified by <code>highWaterMark</code>, the stream will temporarily stop reading data from the underlying resource until the data currently buffered can be consumed (that is, the stream will stop calling the internal <code>readable._read()</code> method that is used to fill the read buffer).</p> <p>Data is buffered in <code>Writable</code> streams when the <a href="#stream_writable_write_chunk_encoding_callback"><code>writable.write(chunk)</code></a> method is called repeatedly. While the total size of the internal write buffer is below the threshold set by <code>highWaterMark</code>, calls to <code>writable.write()</code> will return <code>true</code>. Once the size of the internal buffer reaches or exceeds the <code>highWaterMark</code>, <code>false</code> will be returned.</p> <p>A key goal of the <code>stream</code> API, particularly the <a href="#stream_readable_pipe_destination_options"><code>stream.pipe()</code></a> method, is to limit the buffering of data to acceptable levels such that sources and destinations of differing speeds will not overwhelm the available memory.</p> <p>Because <a href="#stream_class_stream_duplex"><code>Duplex</code></a> and <a href="#stream_class_stream_transform"><code>Transform</code></a> streams are both <code>Readable</code> and <code>Writable</code>, each maintains <em>two</em> separate internal buffers used for reading and writing, allowing each side to operate independently of the other while maintaining an appropriate and efficient flow of data. For example, <a href="https://nodejs.org/api/net.html#net_class_net_socket"><code>net.Socket</code></a> instances are <a href="#stream_class_stream_duplex"><code>Duplex</code></a> streams whose <code>Readable</code> side allows consumption of data received <em>from</em> the socket and whose <code>Writable</code> side allows writing data <em>to</em> the socket. Because data may be written to the socket at a faster or slower rate than data is received, it is important for each side to operate (and buffer) independently of the other.</p> <h2>API for Stream Consumers<span><a class="mark" href="#stream_api_for_stream_consumers" id="stream_api_for_stream_consumers">#</a></span></h2> <p>Almost all Node.js applications, no matter how simple, use streams in some manner. The following is an example of using streams in a Node.js application that implements an HTTP server:</p> <pre><code class="language-js">const http = require('http'); const server = http.createServer((req, res) => { // `req` is an http.IncomingMessage, which is a Readable Stream. // `res` is an http.ServerResponse, which is a Writable Stream. let body = ''; // Get the data as utf8 strings. // If an encoding is not set, Buffer objects will be received. req.setEncoding('utf8'); // Readable streams emit 'data' events once a listener is added. req.on('data', (chunk) => { body += chunk; }); // The 'end' event indicates that the entire body has been received. req.on('end', () => { try { const data = JSON.parse(body); // Write back something interesting to the user: res.write(typeof data); res.end(); } catch (er) { // uh oh! bad json! res.statusCode = 400; return res.end(`error: ${er.message}`); } }); }); server.listen(1337); // $ curl localhost:1337 -d "{}" // object // $ curl localhost:1337 -d "\"foo\"" // string // $ curl localhost:1337 -d "not json" // error: Unexpected token o in JSON at position 1 </code></pre> <p><a href="#stream_class_stream_writable"><code>Writable</code></a> streams (such as <code>res</code> in the example) expose methods such as <code>write()</code> and <code>end()</code> that are used to write data onto the stream.</p> <p><a href="#stream_class_stream_readable"><code>Readable</code></a> streams use the <a href="https://nodejs.org/api/events.html#events_class_eventemitter"><code>EventEmitter</code></a> API for notifying application code when data is available to be read off the stream. That available data can be read from the stream in multiple ways.</p> <p>Both <a href="#stream_class_stream_writable"><code>Writable</code></a> and <a href="#stream_class_stream_readable"><code>Readable</code></a> streams use the <a href="https://nodejs.org/api/events.html#events_class_eventemitter"><code>EventEmitter</code></a> API in various ways to communicate the current state of the stream.</p> <p><a href="#stream_class_stream_duplex"><code>Duplex</code></a> and <a href="#stream_class_stream_transform"><code>Transform</code></a> streams are both <a href="#stream_class_stream_writable"><code>Writable</code></a> and <a href="#stream_class_stream_readable"><code>Readable</code></a>.</p> <p>Applications that are either writing data to or consuming data from a stream are not required to implement the stream interfaces directly and will generally have no reason to call <code>require('stream')</code>.</p> <p>Developers wishing to implement new types of streams should refer to the section <a href="#stream_api_for_stream_implementers">API for Stream Implementers</a>.</p> <h3>Writable Streams<span><a class="mark" href="#stream_writable_streams" id="stream_writable_streams">#</a></span></h3> <p>Writable streams are an abstraction for a <em>destination</em> to which data is written.</p> <p>Examples of <a href="#stream_class_stream_writable"><code>Writable</code></a> streams include:</p> <ul> <li><a href="https://nodejs.org/api/http.html#http_class_http_clientrequest">HTTP requests, on the client</a></li> <li><a href="https://nodejs.org/api/http.html#http_class_http_serverresponse">HTTP responses, on the server</a></li> <li><a href="https://nodejs.org/api/fs.html#fs_class_fs_writestream">fs write streams</a></li> <li><a href="https://nodejs.org/api/zlib.html">zlib streams</a></li> <li><a href="https://nodejs.org/api/crypto.html">crypto streams</a></li> <li><a href="https://nodejs.org/api/net.html#net_class_net_socket">TCP sockets</a></li> <li><a href="https://nodejs.org/api/child_process.html#child_process_subprocess_stdin">child process stdin</a></li> <li><a href="https://nodejs.org/api/process.html#process_process_stdout"><code>process.stdout</code></a>, <a href="https://nodejs.org/api/process.html#process_process_stderr"><code>process.stderr</code></a></li> </ul> <p>Some of these examples are actually <a href="#stream_class_stream_duplex"><code>Duplex</code></a> streams that implement the <a href="#stream_class_stream_writable"><code>Writable</code></a> interface.</p> <p>All <a href="#stream_class_stream_writable"><code>Writable</code></a> streams implement the interface defined by the <code>stream.Writable</code> class.</p> <p>While specific instances of <a href="#stream_class_stream_writable"><code>Writable</code></a> streams may differ in various ways, all <code>Writable</code> streams follow the same fundamental usage pattern as illustrated in the example below:</p> <pre><code class="language-js">const myStream = getWritableStreamSomehow(); myStream.write('some data'); myStream.write('some more data'); myStream.end('done writing data'); </code></pre> <h4>Class: stream.Writable<span><a class="mark" href="#stream_class_stream_writable" id="stream_class_stream_writable">#</a></span></h4> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <h5>Event: 'close'<span><a class="mark" href="#stream_event_close" id="stream_event_close">#</a></span></h5> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tbody><tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Add <code>emitClose</code> option to specify if <code>'close'</code> is emitted on destroy.</p></td></tr> <tr><td>v0.9.4</td> <td><p><span>Added in: v0.9.4</span></p></td></tr> </tbody></table> </details> </div> <p>The <code>'close'</code> event is emitted when the stream and any of its underlying resources (a file descriptor, for example) have been closed. The event indicates that no more events will be emitted, and no further computation will occur.</p> <p>A <a href="#stream_class_stream_writable"><code>Writable</code></a> stream will always emit the <code>'close'</code> event if it is created with the <code>emitClose</code> option.</p> <h5>Event: 'drain'<span><a class="mark" href="#stream_event_drain" id="stream_event_drain">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <p>If a call to <a href="#stream_writable_write_chunk_encoding_callback"><code>stream.write(chunk)</code></a> returns <code>false</code>, the <code>'drain'</code> event will be emitted when it is appropriate to resume writing data to the stream.</p> <pre><code class="language-js">// Write the data to the supplied writable stream one million times. // Be attentive to back-pressure. function writeOneMillionTimes(writer, data, encoding, callback) { let i = 1000000; write(); function write() { let ok = true; do { i--; if (i === 0) { // Last time! writer.write(data, encoding, callback); } else { // See if we should continue, or wait. // Don't pass the callback, because we're not done yet. ok = writer.write(data, encoding); } } while (i > 0 && ok); if (i > 0) { // Had to stop early! // Write some more once it drains. writer.once('drain', write); } } } </code></pre> <h5>Event: 'error'<span><a class="mark" href="#stream_event_error" id="stream_event_error">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error" class="type"><Error></a></li> </ul> <p>The <code>'error'</code> event is emitted if an error occurred while writing or piping data. The listener callback is passed a single <code>Error</code> argument when called.</p> <p>The stream is not closed when the <code>'error'</code> event is emitted unless the <a href="#stream_constructor_new_stream_writable_options"><code>autoDestroy</code></a> option was set to <code>true</code> when creating the stream.</p> <h5>Event: 'finish'<span><a class="mark" href="#stream_event_finish" id="stream_event_finish">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <p>The <code>'finish'</code> event is emitted after the <a href="#stream_writable_end_chunk_encoding_callback"><code>stream.end()</code></a> method has been called, and all data has been flushed to the underlying system.</p> <pre><code class="language-js">const writer = getWritableStreamSomehow(); for (let i = 0; i < 100; i++) { writer.write(`hello, #${i}!\n`); } writer.end('This is the end\n'); writer.on('finish', () => { console.log('All writes are now complete.'); }); </code></pre> <h5>Event: 'pipe'<span><a class="mark" href="#stream_event_pipe" id="stream_event_pipe">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <ul> <li><code>src</code> <a href="https://nodejs.org/api/stream.html#stream_class_stream_readable" class="type"><stream.Readable></a> source stream that is piping to this writable</li> </ul> <p>The <code>'pipe'</code> event is emitted when the <a href="#stream_readable_pipe_destination_options"><code>stream.pipe()</code></a> method is called on a readable stream, adding this writable to its set of destinations.</p> <pre><code class="language-js">const writer = getWritableStreamSomehow(); const reader = getReadableStreamSomehow(); writer.on('pipe', (src) => { console.log('Something is piping into the writer.'); assert.equal(src, reader); }); reader.pipe(writer); </code></pre> <h5>Event: 'unpipe'<span><a class="mark" href="#stream_event_unpipe" id="stream_event_unpipe">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.9.4</span> </div> <ul> <li><code>src</code> <a href="https://nodejs.org/api/stream.html#stream_class_stream_readable" class="type"><stream.Readable></a> The source stream that <a href="#stream_readable_unpipe_destination">unpiped</a> this writable</li> </ul> <p>The <code>'unpipe'</code> event is emitted when the <a href="#stream_readable_unpipe_destination"><code>stream.unpipe()</code></a> method is called on a <a href="#stream_class_stream_readable"><code>Readable</code></a> stream, removing this <a href="#stream_class_stream_writable"><code>Writable</code></a> from its set of destinations.</p> <p>This is also emitted in case this <a href="#stream_class_stream_writable"><code>Writable</code></a> stream emits an error when a <a href="#stream_class_stream_readable"><code>Readable</code></a> stream pipes into it.</p> <pre><code class="language-js">const writer = getWritableStreamSomehow(); const reader = getReadableStreamSomehow(); writer.on('unpipe', (src) => { console.log('Something has stopped piping into the writer.'); assert.equal(src, reader); }); reader.pipe(writer); reader.unpipe(writer); </code></pre> <h5>writable.cork()<span><a class="mark" href="#stream_writable_cork" id="stream_writable_cork">#</a></span></h5> <div class="api_metadata"> <span>Added in: v0.11.2</span> </div> <p>The <code>writable.cork()</code> method forces all written data to be buffered in memory. The buffered data will be flu