Node http.IncomingMessage class | API Reference | Bun

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class

http.IncomingMessageclass IncomingMessageAn IncomingMessage object is created by Server or ClientRequest and passed as the first argument to the 'request' and 'response' event respectively. It may be used to access response status, headers, and data.

Different from its socket value which is a subclass of stream.Duplex, the IncomingMessage itself extends stream.Readable and is created separately to parse and emit the incoming HTTP headers and payload, as the underlying socket may be reused multiple times in case of keep-alive.

readonly closed: booleanIs true after 'close' has been emitted.

{ res.resume(); res.on('end', () => { if (!res.complete) console.error( 'The connection was terminated while the message was still being sent'); }); }); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Property">complete: booleanThe message.complete property will be true if a complete HTTP message has been received and successfully parsed.

This property is particularly useful as a means of determining if a client or server fully transmitted a message before a connection was terminated:

const req = http.request({ host: '127.0.0.1', port: 8080, method: 'POST', }, (res) => { res.resume(); res.on('end', () => { if (!res.complete) console.error( 'The connection was terminated while the message was still being sent'); }); }); destroyed: booleanIs true after readable.destroy() has been called.

readonly errored: null | ErrorReturns error if the stream has been destroyed with an error.

headers: IncomingHttpHeadersThe request/response headers object.

Key-value pairs of header names and values. Header names are lower-cased.

// Prints something like: http:// // { 'user-agent': 'curl/7.22.0', // host: '127.0.0.1:8000', // accept: '*' } console.log(request.headers); Duplicates in raw headers are handled in the following ways, depending on the header name:

Duplicates of age, authorization, content-length, content-type, etag, expires, from, host, if-modified-since, if-unmodified-since, last-modified, location, max-forwards, proxy-authorization, referer, retry-after, server, or user-agent are discarded. To allow duplicate values of the headers listed above to be joined, use the option joinDuplicateHeaders in request and createServer. See RFC 9110 Section 5.3 for more information.set-cookie is always an array. Duplicates are added to the array.For duplicate cookie headers, the values are joined together with ; .For all other headers, the values are joined together with , .headersDistinct: Dictstring[]>Similar to message.headers, but there is no join logic and the values are always arrays of strings, even for headers received just once.

// Prints something like: http:// // { 'user-agent': ['curl/7.22.0'], // host: ['127.0.0.1:8000'], // accept: ['*'] } console.log(request.headersDistinct); httpVersion: stringIn case of server request, the HTTP version sent by the client. In the case of client response, the HTTP version of the connected-to server. Probably either '1.1' or '1.0'.

Also message.httpVersionMajor is the first integer and message.httpVersionMinor is the second.

httpVersionMajor: numberhttpVersionMinor: numbermethod?: stringOnly valid for request obtained from Server.

The request method as a string. Read only. Examples: 'GET', 'DELETE'.

rawHeaders: string[]The raw request/response headers list exactly as they were received.

The keys and values are in the same list. It is not a list of tuples. So, the even-numbered offsets are key values, and the odd-numbered offsets are the associated values.

Header names are not lowercased, and duplicates are not merged.

// Prints something like: http:// // [ 'user-agent', // 'this is invalid because there can be only one', // 'User-Agent', // 'curl/7.22.0', // 'Host', // '127.0.0.1:8000', // 'ACCEPT', // '*' ] console.log(request.rawHeaders); rawTrailers: string[]The raw request/response trailer keys and values exactly as they were received. Only populated at the 'end' event.

readable: booleanIs true if it is safe to call read, which means the stream has not been destroyed or emitted 'error' or 'end'.

readonly readableAborted: booleanReturns whether the stream was destroyed or errored before emitting 'end'.

readonly readableDidRead: booleanReturns whether 'data' has been emitted.

readonly readableEncoding: null | BufferEncodingGetter for the property encoding of a given Readable stream. The encoding property can be set using the setEncoding method.

readonly readableEnded: booleanBecomes true when 'end' event is emitted.

readableFlowing: null | booleanThis property reflects the current state of a Readable stream as described in the Three states section.

readonly readableHighWaterMark: numberReturns the value of highWaterMark passed when creating this Readable.

readonly readableLength: numberThis property contains the number of bytes (or objects) in the queue ready to be read. The value provides introspection data regarding the status of the highWaterMark.

readonly readableObjectMode: booleanGetter for the property objectMode of a given Readable stream.

socket: SocketThe net.Socket object associated with the connection.

With HTTPS support, use request.socket.getPeerCertificate() to obtain the client's authentication details.

This property is guaranteed to be an instance of the net.Socket class, a subclass of stream.Duplex, unless the user specified a socket type other than net.Socket or internally nulled.

statusCode?: numberOnly valid for response obtained from ClientRequest.

The 3-digit HTTP response status code. E.G. 404.

statusMessage?: stringOnly valid for response obtained from ClientRequest.

The HTTP response status message (reason phrase). E.G. OK or Internal Server Error.

trailers: Dictstring>The request/response trailers object. Only populated at the 'end' event.

trailersDistinct: Dictstring[]>Similar to message.trailers, but there is no join logic and the values are always arrays of strings, even for headers received just once. Only populated at the 'end' event.

new URL(`http://${process.env.HOST ?? 'localhost'}${request.url}`); URL { href: 'http://localhost/status?name=ryan', origin: 'http://localhost', protocol: 'http:', username: '', password: '', host: 'localhost', hostname: 'localhost', port: '', pathname: '/status', search: '?name=ryan', searchParams: URLSearchParams { 'name' => 'ryan' }, hash: '' } ``` Ensure that you set `process.env.HOST` to the server's host name, or consider replacing this part entirely. If using `req.headers.host`, ensure proper validation is used, as clients may specify a custom `Host` header." data-algolia-static="false" data-algolia-merged="false" data-type="Property">url?: stringOnly valid for request obtained from Server.

Request URL string. This contains only the URL that is present in the actual HTTP request. Take the following request:

GET /status?name=ryan HTTP/1.1 Accept: text/plain To parse the URL into its parts:

new URL(`http://${process.env.HOST ?? 'localhost'}${request.url}`); When request.url is '/status?name=ryan' and process.env.HOST is undefined:

$ node > new URL(`http://${process.env.HOST ?? 'localhost'}${request.url}`); URL { href: 'http://localhost/status?name=ryan', origin: 'http://localhost', protocol: 'http:', username: '', password: '', host: 'localhost', hostname: 'localhost', port: '', pathname: '/status', search: '?name=ryan', searchParams: URLSearchParams { 'name' => 'ryan' }, hash: '' } Ensure that you set process.env.HOST to the server's host name, or consider replacing this part entirely. If using req.headers.host, ensure proper validation is used, as clients may specify a custom Host header.

_construct(callback: (error?: null | Error) => void): void;_destroy(error: null | Error,callback: (error?: null | Error) => void): void;_read(size: number): void;[Symbol.asyncDispose](): Promisevoid>;Calls readable.destroy() with an AbortError and returns a promise that fulfills when the stream is finished.

[Symbol.asyncIterator](): AsyncIteratorany>;@returnsAsyncIterator to fully consume the stream.

[events.captureRejectionSymbol](error: Error,event: string | symbol,...args: any[]): void;The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

import { EventEmitter, captureRejectionSymbol } from 'node:events'; class MyClass extends EventEmitter { constructor() { super({ captureRejections: true }); } [captureRejectionSymbol](err, event, ...args) { console.log('rejection happened for', event, 'with', err, ...args); this.destroy(err); } destroy(err) { // Tear the resource down here. } } addListenerE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Alias for emitter.on(eventName, listener).

addListener(eventName: string | symbol,listener: (...args: any[]) => void): this;compose(stream: WritableStream | WritableStreamany> | TransformStreamany, any> | (source: any) => void,options?: Abortable): Duplex;import { Readable } from 'node:stream'; async function* splitToWords(source) { for await (const chunk of source) { const words = String(chunk).split(' '); for (const word of words) { yield word; } } } const wordsStream = Readable.from(['this is', 'compose as operator']).compose(splitToWords); const words = await wordsStream.toArray(); console.log(words); // prints ['this', 'is', 'compose', 'as', 'operator'] See stream.compose for more information.

@returnsa stream composed with the stream stream.

destroy(error?: Error): this;Calls destroy() on the socket that received the IncomingMessage. If error is provided, an 'error' event is emitted on the socket and error is passed as an argument to any listeners on the event.

drop(limit: number,options?: Abortable): Readable;This method returns a new stream with the first limit chunks dropped from the start.

@param limitthe number of chunks to drop from the readable.

@returnsa stream with limit chunks dropped from the start.

emitE extends keyof IncomingMessageEventMap>(eventName: E,...args: IncomingMessageEventMap[E]): boolean;Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events'; const myEmitter = new EventEmitter(); // First listener myEmitter.on('event', function firstListener() { console.log('Helloooo! first listener'); }); // Second listener myEmitter.on('event', function secondListener(arg1, arg2) { console.log(`event with parameters ${arg1}, ${arg2} in second listener`); }); // Third listener myEmitter.on('event', function thirdListener(...args) { const parameters = args.join(', '); console.log(`event with parameters ${parameters} in third listener`); }); console.log(myEmitter.listeners('event')); myEmitter.emit('event', 1, 2, 3, 4, 5); // Prints: // [ // [Function: firstListener], // [Function: secondListener], // [Function: thirdListener] // ] // Helloooo! first listener // event with parameters 1, 2 in second listener // event with parameters 1, 2, 3, 4, 5 in third listener emit(eventName: string | symbol,...args: any[]): boolean; {}); myEE.on('bar', () => {}); const sym = Symbol('symbol'); myEE.on(sym, () => {}); console.log(myEE.eventNames()); // Prints: [ 'foo', 'bar', Symbol(symbol) ] ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">eventNames(): string | symbol[];Returns an array listing the events for which the emitter has registered listeners.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => {}); myEE.on('bar', () => {}); const sym = Symbol('symbol'); myEE.on(sym, () => {}); console.log(myEE.eventNames()); // Prints: [ 'foo', 'bar', Symbol(symbol) ] every(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseboolean>;This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to true if fn returned a truthy value for every one of the chunks.

filter(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: ReadableOperatorOptions): Readable;This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.

@param fna function to filter chunks from the stream. Async or not.

@returnsa stream filtered with the predicate fn.

findT>(fn: (data: any, options?: Abortable) => data is T,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseundefined | T>;This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

find(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseany>;This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

flatMap(fn: (data: any, options?: Abortable) => any,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Readable;This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

@param fna function to map over every chunk in the stream. May be async. May be a stream or generator.

@returnsa stream flat-mapped with the function fn.

forEach(fn: (data: any, options?: Abortable) => void | Promisevoid>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promisevoid>;This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.

This method is different from for await...of loops in that it can optionally process chunks concurrently. In addition, a forEach iteration can only be stopped by having passed a signal option and aborting the related AbortController while for await...of can be stopped with break or return. In either case the stream will be destroyed.

This method is different from listening to the 'data' event in that it uses the readable event in the underlying machinary and can limit the number of concurrent fn calls.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise for when the stream has finished.

getMaxListeners(): number;Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to events.defaultMaxListeners.

isPaused(): boolean;The readable.isPaused() method returns the current operating state of the Readable. This is used primarily by the mechanism that underlies the readable.pipe() method. In most typical cases, there will be no reason to use this method directly.

const readable = new stream.Readable(); readable.isPaused(); // === false readable.pause(); readable.isPaused(); // === true readable.resume(); readable.isPaused(); // === false iterator(options?: ReadableIteratorOptions): AsyncIteratorany>;The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.

listenerCountE extends keyof IncomingMessageEventMap>(eventName: E,listener?: (...args: IncomingMessageEventMap[E]) => void): number;Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

@param eventNameThe name of the event being listened for

@param listenerThe event handler function

listenerCount(eventName: string | symbol,listener?: (...args: any[]) => void): number; { console.log('someone connected!'); }); console.log(util.inspect(server.listeners('connection'))); // Prints: [ [Function] ] ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">listenersE extends keyof IncomingMessageEventMap>(eventName: E): (...args: IncomingMessageEventMap[E]) => void[];Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => { console.log('someone connected!'); }); console.log(util.inspect(server.listeners('connection'))); // Prints: [ [Function] ] listeners(eventName: string | symbol): (...args: any[]) => void[];map(fn: (data: any, options?: Abortable) => any,options?: ReadableOperatorOptions): Readable;This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.

@param fna function to map over every chunk in the stream. Async or not.

@returnsa stream mapped with the function fn.

offE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Alias for emitter.removeListener().

off(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('someone connected!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained. By default, event listeners are invoked in the order they are added. The `emitter.prependListener()` method can be used as an alternative to add the event listener to the beginning of the listeners array. ```js import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => console.log('a')); myEE.prependListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">onE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.on('connection', (stream) => { console.log('someone connected!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.on('foo', () => console.log('a')); myEE.prependListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a @param eventNameThe name of the event.

@param listenerThe callback function

on(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('Ah, we have our first user!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained. By default, event listeners are invoked in the order they are added. The `emitter.prependOnceListener()` method can be used as an alternative to add the event listener to the beginning of the listeners array. ```js import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.once('foo', () => console.log('a')); myEE.prependOnceListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">onceE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => { console.log('Ah, we have our first user!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events'; const myEE = new EventEmitter(); myEE.once('foo', () => console.log('a')); myEE.prependOnceListener('foo', () => console.log('b')); myEE.emit('foo'); // Prints: // b // a @param eventNameThe name of the event.

@param listenerThe callback function

once(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log(`Received ${chunk.length} bytes of data.`); readable.pause(); console.log('There will be no additional data for 1 second.'); setTimeout(() => { console.log('Now data will start flowing again.'); readable.resume(); }, 1000); }); ``` The `readable.pause()` method has no effect if there is a `'readable'` event listener." data-algolia-static="false" data-algolia-merged="false" data-type="Method">pause(): this;The readable.pause() method will cause a stream in flowing mode to stop emitting 'data' events, switching out of flowing mode. Any data that becomes available will remain in the internal buffer.

const readable = getReadableStreamSomehow(); readable.on('data', (chunk) => { console.log(`Received ${chunk.length} bytes of data.`); readable.pause(); console.log('There will be no additional data for 1 second.'); setTimeout(() => { console.log('Now data will start flowing again.'); readable.resume(); }, 1000); }); The readable.pause() method has no effect if there is a 'readable' event listener.

pipeT extends WritableStream>(destination: T,options?: PipeOptions): T; { console.log('someone connected!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">prependListenerE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => { console.log('someone connected!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

@param eventNameThe name of the event.

@param listenerThe callback function

prependListener(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('Ah, we have our first user!'); }); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">prependOnceListenerE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Adds a one-time listener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => { console.log('Ah, we have our first user!'); }); Returns a reference to the EventEmitter, so that calls can be chained.

@param eventNameThe name of the event.

@param listenerThe callback function

prependOnceListener(eventName: string | symbol,listener: (...args: any[]) => void): this;push(chunk: any,encoding?: BufferEncoding): boolean; console.log('log once')); // Returns a new Array with a function `onceWrapper` which has a property // `listener` which contains the original listener bound above const listeners = emitter.rawListeners('log'); const logFnWrapper = listeners[0]; // Logs "log once" to the console and does not unbind the `once` event logFnWrapper.listener(); // Logs "log once" to the console and removes the listener logFnWrapper(); emitter.on('log', () => console.log('log persistently')); // Will return a new Array with a single function bound by `.on()` above const newListeners = emitter.rawListeners('log'); // Logs "log persistently" twice newListeners[0](); emitter.emit('log'); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">rawListenersE extends keyof IncomingMessageEventMap>(eventName: E): (...args: IncomingMessageEventMap[E]) => void[];Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events'; const emitter = new EventEmitter(); emitter.once('log', () => console.log('log once')); // Returns a new Array with a function `onceWrapper` which has a property // `listener` which contains the original listener bound above const listeners = emitter.rawListeners('log'); const logFnWrapper = listeners[0]; // Logs "log once" to the console and does not unbind the `once` event logFnWrapper.listener(); // Logs "log once" to the console and removes the listener logFnWrapper(); emitter.on('log', () => console.log('log persistently')); // Will return a new Array with a single function bound by `.on()` above const newListeners = emitter.rawListeners('log'); // Logs "log persistently" twice newListeners[0](); emitter.emit('log'); rawListeners(eventName: string | symbol): (...args: any[]) => void[]; { let chunk; console.log('Stream is readable (new data received in buffer)'); // Use a loop to make sure we read all currently available data while (null !== (chunk = readable.read())) { console.log(`Read ${chunk.length} bytes of data...`); } }); // 'end' will be triggered once when there is no more data available readable.on('end', () => { console.log('Reached end of stream.'); }); ``` Each call to `readable.read()` returns a chunk of data, or `null`. The chunks are not concatenated. A `while` loop is necessary to consume all data currently in the buffer. When reading a large file `.read()` may return `null`, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new `'readable'` event will be emitted when there is more data in the buffer. Finally the `'end'` event will be emitted when there is no more data to come. Therefore to read a file's whole contents from a `readable`, it is necessary to collect chunks across multiple `'readable'` events: ```js const chunks = []; readable.on('readable', () => { let chunk; while (null !== (chunk = readable.read())) { chunks.push(chunk); } }); readable.on('end', () => { const content = chunks.join(''); }); ``` A `Readable` stream in object mode will always return a single item from a call to `readable.read(size)`, regardless of the value of the `size` argument. If the `readable.read()` method returns a chunk of data, a `'data'` event will also be emitted. Calling read after the `'end'` event has been emitted will return `null`. No runtime error will be raised." data-algolia-static="false" data-algolia-merged="false" data-type="Method">read(size?: number): any;The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.

The optional size argument specifies a specific number of bytes to read. If size bytes are not available to be read, null will be returned unless the stream has ended, in which case all of the data remaining in the internal buffer will be returned.

If the size argument is not specified, all of the data contained in the internal buffer will be returned.

The size argument must be less than or equal to 1 GiB.

The readable.read() method should only be called on Readable streams operating in paused mode. In flowing mode, readable.read() is called automatically until the internal buffer is fully drained.

const readable = getReadableStreamSomehow(); // 'readable' may be triggered multiple times as data is buffered in readable.on('readable', () => { let chunk; console.log('Stream is readable (new data received in buffer)'); // Use a loop to make sure we read all currently available data while (null !== (chunk = readable.read())) { console.log(`Read ${chunk.length} bytes of data...`); } }); // 'end' will be triggered once when there is no more data available readable.on('end', () => { console.log('Reached end of stream.'); }); Each call to readable.read() returns a chunk of data, or null. The chunks are not concatenated. A while loop is necessary to consume all data currently in the buffer. When reading a large file .read() may return null, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new 'readable' event will be emitted when there is more data in the buffer. Finally the 'end' event will be emitted when there is no more data to come.

Therefore to read a file's whole contents from a readable, it is necessary to collect chunks across multiple 'readable' events:

const chunks = []; readable.on('readable', () => { let chunk; while (null !== (chunk = readable.read())) { chunks.push(chunk); } }); readable.on('end', () => { const content = chunks.join(''); }); A Readable stream in object mode will always return a single item from a call to readable.read(size), regardless of the value of the size argument.

If the readable.read() method returns a chunk of data, a 'data' event will also be emitted.

Calling read after the 'end' event has been emitted will return null. No runtime error will be raised.

@param sizeOptional argument to specify how much data to read.

reduceT>(fn: (previous: any, data: any, options?: Abortable) => T): PromiseT>;This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

@param fna reducer function to call over every chunk in the stream. Async or not.

@returnsa promise for the final value of the reduction.

reduceT>(fn: (previous: T, data: any, options?: Abortable) => T,initial: T,options?: Abortable): PromiseT>;This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

@param fna reducer function to call over every chunk in the stream. Async or not.

@param initialthe initial value to use in the reduction.

@returnsa promise for the final value of the reduction.

removeAllListenersE extends keyof IncomingMessageEventMap>(eventName?: E): this;Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

removeAllListeners(eventName?: string | symbol): this; { console.log('someone connected!'); }; server.on('connection', callback); // ... server.removeListener('connection', callback); ``` `removeListener()` will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified `eventName`, then `removeListener()` must be called multiple times to remove each instance. Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any `removeListener()` or `removeAllListeners()` calls _after_ emitting and _before_ the last listener finishes execution will not remove them from `emit()` in progress. Subsequent events behave as expected. ```js import { EventEmitter } from 'node:events'; class MyEmitter extends EventEmitter {} const myEmitter = new MyEmitter(); const callbackA = () => { console.log('A'); myEmitter.removeListener('event', callbackB); }; const callbackB = () => { console.log('B'); }; myEmitter.on('event', callbackA); myEmitter.on('event', callbackB); // callbackA removes listener callbackB but it will still be called. // Internal listener array at time of emit [callbackA, callbackB] myEmitter.emit('event'); // Prints: // A // B // callbackB is now removed. // Internal listener array [callbackA] myEmitter.emit('event'); // Prints: // A ``` Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered _after_ the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the `emitter.listeners()` method will need to be recreated. When a single function has been added as a handler multiple times for a single event (as in the example below), `removeListener()` will remove the most recently added instance. In the example the `once('ping')` listener is removed: ```js import { EventEmitter } from 'node:events'; const ee = new EventEmitter(); function pong() { console.log('pong'); } ee.on('ping', pong); ee.once('ping', pong); ee.removeListener('ping', pong); ee.emit('ping'); ee.emit('ping'); ``` Returns a reference to the `EventEmitter`, so that calls can be chained." data-algolia-static="false" data-algolia-merged="false" data-type="Method">removeListenerE extends keyof IncomingMessageEventMap>(eventName: E,listener: (...args: IncomingMessageEventMap[E]) => void): this;Removes the specified listener from the listener array for the event named eventName.

const callback = (stream) => { console.log('someone connected!'); }; server.on('connection', callback); // ... server.removeListener('connection', callback); removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

import { EventEmitter } from 'node:events'; class MyEmitter extends EventEmitter {} const myEmitter = new MyEmitter(); const callbackA = () => { console.log('A'); myEmitter.removeListener('event', callbackB); }; const callbackB = () => { console.log('B'); }; myEmitter.on('event', callbackA); myEmitter.on('event', callbackB); // callbackA removes listener callbackB but it will still be called. // Internal listener array at time of emit [callbackA, callbackB] myEmitter.emit('event'); // Prints: // A // B // callbackB is now removed. // Internal listener array [callbackA] myEmitter.emit('event'); // Prints: // A Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

import { EventEmitter } from 'node:events'; const ee = new EventEmitter(); function pong() { console.log('pong'); } ee.on('ping', pong); ee.once('ping', pong); ee.removeListener('ping', pong); ee.emit('ping'); ee.emit('ping'); Returns a reference to the EventEmitter, so that calls can be chained.

removeListener(eventName: string | symbol,listener: (...args: any[]) => void): this; { console.log('Reached the end, but did not read anything.'); }); ``` The `readable.resume()` method has no effect if there is a `'readable'` event listener." data-algolia-static="false" data-algolia-merged="false" data-type="Method">resume(): this;The readable.resume() method causes an explicitly paused Readable stream to resume emitting 'data' events, switching the stream into flowing mode.

The readable.resume() method can be used to fully consume the data from a stream without actually processing any of that data:

getReadableStreamSomehow() .resume() .on('end', () => { console.log('Reached the end, but did not read anything.'); }); The readable.resume() method has no effect if there is a 'readable' event listener.

{ assert.equal(typeof chunk, 'string'); console.log('Got %d characters of string data:', chunk.length); }); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">setEncoding(encoding: BufferEncoding): this;The readable.setEncoding() method sets the character encoding for data read from the Readable stream.

By default, no encoding is assigned and stream data will be returned as Buffer objects. Setting an encoding causes the stream data to be returned as strings of the specified encoding rather than as Buffer objects. For instance, calling readable.setEncoding('utf8') will cause the output data to be interpreted as UTF-8 data, and passed as strings. Calling readable.setEncoding('hex') will cause the data to be encoded in hexadecimal string format.

The Readable stream will properly handle multi-byte characters delivered through the stream that would otherwise become improperly decoded if simply pulled from the stream as Buffer objects.

const readable = getReadableStreamSomehow(); readable.setEncoding('utf8'); readable.on('data', (chunk) => { assert.equal(typeof chunk, 'string'); console.log('Got %d characters of string data:', chunk.length); }); @param encodingThe encoding to use.

setMaxListeners(n: number): this;By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

setTimeout(msecs: number,callback?: () => void): this;Calls message.socket.setTimeout(msecs, callback).

some(fn: (data: any, options?: Abortable) => boolean | Promiseboolean>,options?: PickReadableOperatorOptions, 'signal' | 'concurrency'>): Promiseboolean>;This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.

@param fna function to call on each chunk of the stream. Async or not.

@returnsa promise evaluating to true if fn returned a truthy value for at least one of the chunks.

take(limit: number,options?: Abortable): Readable;This method returns a new stream with the first limit chunks.

@param limitthe number of chunks to take from the readable.

@returnsa stream with limit chunks taken.

toArray(options?: Abortable): Promiseany[]>;This method allows easily obtaining the contents of a stream.

As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.

@returnsa promise containing an array with the contents of the stream.

{ console.log('Stop writing to file.txt.'); readable.unpipe(writable); console.log('Manually close the file stream.'); writable.end(); }, 1000); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">unpipe(destination?: WritableStream): this;The readable.unpipe() method detaches a Writable stream previously attached using the pipe method.

If the destination is not specified, then all pipes are detached.

If the destination is specified, but no pipe is set up for it, then the method does nothing.

import fs from 'node:fs'; const readable = getReadableStreamSomehow(); const writable = fs.createWriteStream('file.txt'); // All the data from readable goes into 'file.txt', // but only for the first second. readable.pipe(writable); setTimeout(() => { console.log('Stop writing to file.txt.'); readable.unpipe(writable); console.log('Manually close the file stream.'); writable.end(); }, 1000); @param destinationOptional specific stream to unpipe

unshift(chunk: any,encoding?: BufferEncoding): void;Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.

The readable.unshift() method pushes a chunk of data back into the internal buffer. This is useful in certain situations where a stream is being consumed by code that needs to "un-consume" some amount of data that it has optimistically pulled out of the source, so that the data can be passed on to some other party.

The stream.unshift(chunk) method cannot be called after the 'end' event has been emitted or a runtime error will be thrown.

Developers using stream.unshift() often should consider switching to use of a Transform stream instead. See the API for stream implementers section for more information.

// Pull off a header delimited by \n\n. // Use unshift() if we get too much. // Call the callback with (error, header, stream). import { StringDecoder } from 'node:string_decoder'; function parseHeader(stream, callback) { stream.on('error', callback); stream.on('readable', onReadable); const decoder = new StringDecoder('utf8'); let header = ''; function onReadable() { let chunk; while (null !== (chunk = stream.read())) { const str = decoder.write(chunk); if (str.includes('\n\n')) { // Found the header boundary. const split = str.split(/\n\n/); header += split.shift(); const remaining = split.join('\n\n'); const buf = Buffer.from(remaining, 'utf8'); stream.removeListener('error', callback); // Remove the 'readable' listener before unshifting. stream.removeListener('readable', onReadable); if (buf.length) stream.unshift(buf); // Now the body of the message can be read from the stream. callback(null, header, stream); return; } // Still reading the header. header += str; } } } Unlike push, stream.unshift(chunk) will not end the reading process by resetting the internal reading state of the stream. This can cause unexpected results if readable.unshift() is called during a read (i.e. from within a _read implementation on a custom stream). Following the call to readable.unshift() with an immediate push will reset the reading state appropriately, however it is best to simply avoid calling readable.unshift() while in the process of performing a read.

@param chunkChunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a {string}, {Buffer}, {TypedArray}, {DataView} or null. For object mode streams, chunk may be any JavaScript value.

@param encodingEncoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.

{ myReader.read(); // etc. }); ```" data-algolia-static="false" data-algolia-merged="false" data-type="Method">wrap(stream: ReadableStream): this;Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)

When using an older Node.js library that emits 'data' events and has a pause method that is advisory only, the readable.wrap() method can be used to create a Readable stream that uses the old stream as its data source.

It will rarely be necessary to use readable.wrap() but the method has been provided as a convenience for interacting with older Node.js applications and libraries.

import { OldReader } from './old-api-module.js'; import { Readable } from 'node:stream'; const oreader = new OldReader(); const myReader = new Readable().wrap(oreader); myReader.on('readable', () => { myReader.read(); // etc. }); @param streamAn "old style" readable stream

static from(iterable: Iterableany, any, any> | AsyncIterableany, any, any>,options?: ReadableOptionsReadable>): Readable;A utility method for creating Readable Streams out of iterators.

@param iterableObject implementing the Symbol.asyncIterator or Symbol.iterator iterable protocol. Emits an 'error' event if a null value is passed.

@param optionsOptions provided to new stream.Readable([options]). By default, Readable.from() will set options.objectMode to true, unless this is explicitly opted out by setting options.objectMode to false.

static fromWeb(readableStream: ReadableStream,options?: PickReadableOptionsReadable>, 'signal' | 'encoding' | 'highWaterMark' | 'objectMode'>): Readable;A utility method for creating a Readable from a web ReadableStream.

static isDisturbed(stream: ReadableStream | ReadableStreamany>): boolean;Returns whether the stream has been read from or cancelled.

static toWeb(streamReadable: ReadableStream,options?: ReadableToWebOptions): ReadableStream;A utility method for creating a web ReadableStream from a Readable.

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