Bun

class

http2.Http2ServerResponse

class Http2ServerResponse<Request extends Http2ServerRequest = Http2ServerRequest>

This object is created internally by an HTTP server, not by the user. It is passed as the second parameter to the 'request' event.

  • readonly closed: boolean

    Is true after 'close' has been emitted.

  • destroyed: boolean

    Is true after writable.destroy() has been called.

  • readonly errored: null | Error

    Returns error if the stream has been destroyed with an error.

  • readonly headersSent: boolean

    True if headers were sent, false otherwise (read-only).

  • readonly req: Request

    A reference to the original HTTP2 request object.

  • sendDate: boolean

    When true, the Date header will be automatically generated and sent in the response if it is not already present in the headers. Defaults to true.

    This should only be disabled for testing; HTTP requires the Date header in responses.

  • readonly socket: Socket | TLSSocket

    Returns a Proxy object that acts as a net.Socket (or tls.TLSSocket) but applies getters, setters, and methods based on HTTP/2 logic.

    destroyed, readable, and writable properties will be retrieved from and set on response.stream.

    destroy, emit, end, on and once methods will be called on response.stream.

    setTimeout method will be called on response.stream.session.

    pause, read, resume, and write will throw an error with code ERR_HTTP2_NO_SOCKET_MANIPULATION. See Http2Session and Sockets for more information.

    All other interactions will be routed directly to the socket.

    import http2 from 'node:http2';
    const server = http2.createServer((req, res) => {
      const ip = req.socket.remoteAddress;
      const port = req.socket.remotePort;
      res.end(`Your IP address is ${ip} and your source port is ${port}.`);
    }).listen(3000);
    
  • statusCode: number

    When using implicit headers (not calling response.writeHead() explicitly), this property controls the status code that will be sent to the client when the headers get flushed.

    response.statusCode = 404;
    

    After response header was sent to the client, this property indicates the status code which was sent out.

  • statusMessage: ''

    Status message is not supported by HTTP/2 (RFC 7540 8.1.2.4). It returns an empty string.

  • readonly stream: ServerHttp2Stream

    The Http2Stream object backing the response.

  • readonly writable: boolean

    Is true if it is safe to call writable.write(), which means the stream has not been destroyed, errored, or ended.

  • readonly writableCorked: number

    Number of times writable.uncork() needs to be called in order to fully uncork the stream.

  • readonly writableEnded: boolean

    Is true after writable.end() has been called. This property does not indicate whether the data has been flushed, for this use writable.writableFinished instead.

  • readonly writableFinished: boolean

    Is set to true immediately before the 'finish' event is emitted.

  • readonly writableHighWaterMark: number

    Return the value of highWaterMark passed when creating this Writable.

  • readonly writableLength: number

    This property contains the number of bytes (or objects) in the queue ready to be written. The value provides introspection data regarding the status of the highWaterMark.

  • readonly writableNeedDrain: boolean

    Is true if the stream's buffer has been full and stream will emit 'drain'.

  • readonly writableObjectMode: boolean

    Getter for the property objectMode of a given Writable stream.

  • static captureRejections: boolean

    Value: boolean

    Change the default captureRejections option on all new EventEmitter objects.

  • readonly static captureRejectionSymbol: typeof captureRejectionSymbol

    Value: Symbol.for('nodejs.rejection')

    See how to write a custom rejection handler.

  • static defaultMaxListeners: number

    By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListeners property can be used. If this value is not a positive number, a RangeError is thrown.

    Take caution when setting the events.defaultMaxListeners because the change affects all EventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

    This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any single EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to temporarily avoid this warning:

    import { EventEmitter } from 'node:events';
    const emitter = new EventEmitter();
    emitter.setMaxListeners(emitter.getMaxListeners() + 1);
    emitter.once('event', () => {
      // do stuff
      emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
    });
    

    The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

    The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

  • readonly static errorMonitor: typeof errorMonitor

    This symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.

    Installing a listener using this symbol does not change the behavior once an 'error' event is emitted. Therefore, the process will still crash if no regular 'error' listener is installed.

  • callback: (error?: null | Error) => void
    ): void;
  • error: null | Error,
    callback: (error?: null | Error) => void
    ): void;
  • callback: (error?: null | Error) => void
    ): void;
  • chunk: any,
    encoding: BufferEncoding,
    callback: (error?: null | Error) => void
    ): void;
  • chunks: { chunk: any; encoding: BufferEncoding }[],
    callback: (error?: null | Error) => void
    ): void;
  • error: Error,
    event: string | symbol,
    ...args: AnyRest
    ): void;
  • event: 'close',
    listener: () => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: 'drain',
    listener: () => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: 'error',
    listener: (error: Error) => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: 'finish',
    listener: () => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;

    Event emitter The defined events on documents including:

    1. close
    2. drain
    3. error
    4. finish
    5. pipe
    6. unpipe
  • ): void;

    This method adds HTTP trailing headers (a header but at the end of the message) to the response.

    Attempting to set a header field name or value that contains invalid characters will result in a TypeError being thrown.

  • name: string,
    value: string | string[]
    ): void;

    Append a single header value to the header object.

    If the value is an array, this is equivalent to calling this method multiple times.

    If there were no previous values for the header, this is equivalent to calling setHeader.

    Attempting to set a header field name or value that contains invalid characters will result in a TypeError being thrown.

    // Returns headers including "set-cookie: a" and "set-cookie: b"
    const server = http2.createServer((req, res) => {
      res.setHeader('set-cookie', 'a');
      res.appendHeader('set-cookie', 'b');
      res.writeHead(200);
      res.end('ok');
    });
    
  • compose<T extends ReadableStream>(
    stream: ComposeFnParam | T | Iterable<T, any, any> | AsyncIterable<T, any, any>,
    options?: { signal: AbortSignal }
    ): T;
  • cork(): void;

    The writable.cork() method forces all written data to be buffered in memory. The buffered data will be flushed when either the uncork or end methods are called.

    The primary intent of writable.cork() is to accommodate a situation in which several small chunks are written to the stream in rapid succession. Instead of immediately forwarding them to the underlying destination, writable.cork() buffers all the chunks until writable.uncork() is called, which will pass them all to writable._writev(), if present. This prevents a head-of-line blocking situation where data is being buffered while waiting for the first small chunk to be processed. However, use of writable.cork() without implementing writable._writev() may have an adverse effect on throughput.

    See also: writable.uncork(), writable._writev().

  • callback: (err: null | Error, res: Http2ServerResponse) => void
    ): void;

    Call http2stream.pushStream() with the given headers, and wrap the given Http2Stream on a newly created Http2ServerResponse as the callback parameter if successful. When Http2ServerRequest is closed, the callback is called with an error ERR_HTTP2_INVALID_STREAM.

    @param headers

    An object describing the headers

    @param callback

    Called once http2stream.pushStream() is finished, or either when the attempt to create the pushed Http2Stream has failed or has been rejected, or the state of Http2ServerRequest is closed prior to calling the http2stream.pushStream() method

  • error?: Error
    ): this;

    Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the writable stream has ended and subsequent calls to write() or end() will result in an ERR_STREAM_DESTROYED error. This is a destructive and immediate way to destroy a stream. Previous calls to write() may not have drained, and may trigger an ERR_STREAM_DESTROYED error. Use end() instead of destroy if data should flush before close, or wait for the 'drain' event before destroying the stream.

    Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

    Implementors should not override this method, but instead implement writable._destroy().

    @param error

    Optional, an error to emit with 'error' event.

  • event: 'close'
    ): 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
    
    event: 'drain'
    ): boolean;
    event: 'error',
    error: Error
    ): boolean;
    event: 'finish'
    ): boolean;
    event: 'pipe',
    ): boolean;
    event: 'unpipe',
    ): boolean;
    event: string | symbol,
    ...args: any[]
    ): boolean;
  • callback?: () => void
    ): this;

    This method signals to the server that all of the response headers and body have been sent; that server should consider this message complete. The method, response.end(), MUST be called on each response.

    If data is specified, it is equivalent to calling response.write(data, encoding) followed by response.end(callback).

    If callback is specified, it will be called when the response stream is finished.

    data: string | Uint8Array<ArrayBufferLike>,
    callback?: () => void
    ): this;

    This method signals to the server that all of the response headers and body have been sent; that server should consider this message complete. The method, response.end(), MUST be called on each response.

    If data is specified, it is equivalent to calling response.write(data, encoding) followed by response.end(callback).

    If callback is specified, it will be called when the response stream is finished.

    data: string | Uint8Array<ArrayBufferLike>,
    encoding: BufferEncoding,
    callback?: () => void
    ): this;

    This method signals to the server that all of the response headers and body have been sent; that server should consider this message complete. The method, response.end(), MUST be called on each response.

    If data is specified, it is equivalent to calling response.write(data, encoding) followed by response.end(callback).

    If callback is specified, it will be called when the response stream is finished.

  • eventNames(): string | symbol[];

    Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

    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) ]
    
  • name: string
    ): string;

    Reads out a header that has already been queued but not sent to the client. The name is case-insensitive.

    const contentType = response.getHeader('content-type');
    
  • getHeaderNames(): string[];

    Returns an array containing the unique names of the current outgoing headers. All header names are lowercase.

    response.setHeader('Foo', 'bar');
    response.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);
    
    const headerNames = response.getHeaderNames();
    // headerNames === ['foo', 'set-cookie']
    
  • Returns a shallow copy of the current outgoing headers. Since a shallow copy is used, array values may be mutated without additional calls to various header-related http module methods. The keys of the returned object are the header names and the values are the respective header values. All header names are lowercase.

    The object returned by the response.getHeaders() method does not prototypically inherit from the JavaScript Object. This means that typical Object methods such as obj.toString(), obj.hasOwnProperty(), and others are not defined and will not work.

    response.setHeader('Foo', 'bar');
    response.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);
    
    const headers = response.getHeaders();
    // headers === { foo: 'bar', 'set-cookie': ['foo=bar', 'bar=baz'] }
    
  • getMaxListeners(): number;

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

  • name: string
    ): boolean;

    Returns true if the header identified by name is currently set in the outgoing headers. The header name matching is case-insensitive.

    const hasContentType = response.hasHeader('content-type');
    
  • eventName: string | symbol,
    listener?: Function
    ): 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 eventName

    The name of the event being listened for

    @param listener

    The event handler function

  • eventName: string | symbol
    ): Function[];

    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] ]
    
  • off<K>(
    eventName: string | symbol,
    listener: (...args: any[]) => void
    ): this;

    Alias for emitter.removeListener().

  • event: 'close',
    listener: () => 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 listener

    The callback function

    event: 'drain',
    listener: () => void
    ): this;
    event: 'error',
    listener: (error: Error) => void
    ): this;
    event: 'finish',
    listener: () => void
    ): this;
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;
  • event: 'close',
    listener: () => 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 listener

    The callback function

    event: 'drain',
    listener: () => void
    ): this;
    event: 'error',
    listener: (error: Error) => void
    ): this;
    event: 'finish',
    listener: () => void
    ): this;
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;
  • pipe<T extends WritableStream>(
    destination: T,
    options?: { end: boolean }
    ): T;
  • event: 'close',
    listener: () => 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 listener

    The callback function

    event: 'drain',
    listener: () => void
    ): this;
    event: 'error',
    listener: (error: Error) => void
    ): this;
    event: 'finish',
    listener: () => void
    ): this;
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;
  • event: 'close',
    listener: () => void
    ): this;

    Adds a one-timelistener 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 listener

    The callback function

    event: 'drain',
    listener: () => void
    ): this;
    event: 'error',
    listener: (error: Error) => void
    ): this;
    event: 'finish',
    listener: () => void
    ): this;
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;
  • eventName: string | symbol
    ): Function[];

    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');
    
  • eventName?: string | symbol
    ): 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.

  • name: string
    ): void;

    Removes a header that has been queued for implicit sending.

    response.removeHeader('Content-Encoding');
    
  • event: 'close',
    listener: () => 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 fromemit() 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 indices 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.

    event: 'drain',
    listener: () => void
    ): this;
    event: 'error',
    listener: (err: Error) => void
    ): this;
    event: 'finish',
    listener: () => void
    ): this;
    event: 'pipe',
    listener: (src: Readable) => void
    ): this;
    event: 'unpipe',
    listener: (src: Readable) => void
    ): this;
    event: string | symbol,
    listener: (...args: any[]) => void
    ): this;
  • encoding: BufferEncoding
    ): this;

    The writable.setDefaultEncoding() method sets the default encoding for a Writable stream.

    @param encoding

    The new default encoding

  • name: string,
    value: string | number | readonly string[]
    ): void;

    Sets a single header value for implicit headers. If this header already exists in the to-be-sent headers, its value will be replaced. Use an array of strings here to send multiple headers with the same name.

    response.setHeader('Content-Type', 'text/html; charset=utf-8');
    

    or

    response.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);
    

    Attempting to set a header field name or value that contains invalid characters will result in a TypeError being thrown.

    When headers have been set with response.setHeader(), they will be merged with any headers passed to response.writeHead(), with the headers passed to response.writeHead() given precedence.

    // Returns content-type = text/plain
    const server = http2.createServer((req, res) => {
      res.setHeader('Content-Type', 'text/html; charset=utf-8');
      res.setHeader('X-Foo', 'bar');
      res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });
      res.end('ok');
    });
    
  • 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.

  • msecs: number,
    callback?: () => void
    ): void;

    Sets the Http2Stream's timeout value to msecs. If a callback is provided, then it is added as a listener on the 'timeout' event on the response object.

    If no 'timeout' listener is added to the request, the response, or the server, then Http2Stream s are destroyed when they time out. If a handler is assigned to the request, the response, or the server's 'timeout' events, timed out sockets must be handled explicitly.

  • uncork(): void;

    The writable.uncork() method flushes all data buffered since cork was called.

    When using writable.cork() and writable.uncork() to manage the buffering of writes to a stream, defer calls to writable.uncork() using process.nextTick(). Doing so allows batching of all writable.write() calls that occur within a given Node.js event loop phase.

    stream.cork();
    stream.write('some ');
    stream.write('data ');
    process.nextTick(() => stream.uncork());
    

    If the writable.cork() method is called multiple times on a stream, the same number of calls to writable.uncork() must be called to flush the buffered data.

    stream.cork();
    stream.write('some ');
    stream.cork();
    stream.write('data ');
    process.nextTick(() => {
      stream.uncork();
      // The data will not be flushed until uncork() is called a second time.
      stream.uncork();
    });
    

    See also: writable.cork().

  • chunk: string | Uint8Array<ArrayBufferLike>,
    callback?: (err: Error) => void
    ): boolean;

    If this method is called and response.writeHead() has not been called, it will switch to implicit header mode and flush the implicit headers.

    This sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body.

    In the node:http module, the response body is omitted when the request is a HEAD request. Similarly, the 204 and 304 responses must not include a message body.

    chunk can be a string or a buffer. If chunk is a string, the second parameter specifies how to encode it into a byte stream. By default the encoding is 'utf8'. callback will be called when this chunk of data is flushed.

    This is the raw HTTP body and has nothing to do with higher-level multi-part body encodings that may be used.

    The first time response.write() is called, it will send the buffered header information and the first chunk of the body to the client. The second time response.write() is called, Node.js assumes data will be streamed, and sends the new data separately. That is, the response is buffered up to the first chunk of the body.

    Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory.'drain' will be emitted when the buffer is free again.

    chunk: string | Uint8Array<ArrayBufferLike>,
    encoding: BufferEncoding,
    callback?: (err: Error) => void
    ): boolean;

    If this method is called and response.writeHead() has not been called, it will switch to implicit header mode and flush the implicit headers.

    This sends a chunk of the response body. This method may be called multiple times to provide successive parts of the body.

    In the node:http module, the response body is omitted when the request is a HEAD request. Similarly, the 204 and 304 responses must not include a message body.

    chunk can be a string or a buffer. If chunk is a string, the second parameter specifies how to encode it into a byte stream. By default the encoding is 'utf8'. callback will be called when this chunk of data is flushed.

    This is the raw HTTP body and has nothing to do with higher-level multi-part body encodings that may be used.

    The first time response.write() is called, it will send the buffered header information and the first chunk of the body to the client. The second time response.write() is called, Node.js assumes data will be streamed, and sends the new data separately. That is, the response is buffered up to the first chunk of the body.

    Returns true if the entire data was flushed successfully to the kernel buffer. Returns false if all or part of the data was queued in user memory.'drain' will be emitted when the buffer is free again.

  • writeContinue(): void;

    Sends a status 100 Continue to the client, indicating that the request body should be sent. See the 'checkContinue' event on Http2Server and Http2SecureServer.

  • hints: Record<string, string | string[]>
    ): void;

    Sends a status 103 Early Hints to the client with a Link header, indicating that the user agent can preload/preconnect the linked resources. The hints is an object containing the values of headers to be sent with early hints message.

    Example

    const earlyHintsLink = '</styles.css>; rel=preload; as=style';
    response.writeEarlyHints({
      'link': earlyHintsLink,
    });
    
    const earlyHintsLinks = [
      '</styles.css>; rel=preload; as=style',
      '</scripts.js>; rel=preload; as=script',
    ];
    response.writeEarlyHints({
      'link': earlyHintsLinks,
    });
    
  • statusCode: number,
    ): this;

    Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers.

    Returns a reference to the Http2ServerResponse, so that calls can be chained.

    For compatibility with HTTP/1, a human-readable statusMessage may be passed as the second argument. However, because the statusMessage has no meaning within HTTP/2, the argument will have no effect and a process warning will be emitted.

    const body = 'hello world';
    response.writeHead(200, {
      'Content-Length': Buffer.byteLength(body),
      'Content-Type': 'text/plain; charset=utf-8',
    });
    

    Content-Length is given in bytes not characters. TheBuffer.byteLength() API may be used to determine the number of bytes in a given encoding. On outbound messages, Node.js does not check if Content-Length and the length of the body being transmitted are equal or not. However, when receiving messages, Node.js will automatically reject messages when the Content-Length does not match the actual payload size.

    This method may be called at most one time on a message before response.end() is called.

    If response.write() or response.end() are called before calling this, the implicit/mutable headers will be calculated and call this function.

    When headers have been set with response.setHeader(), they will be merged with any headers passed to response.writeHead(), with the headers passed to response.writeHead() given precedence.

    // Returns content-type = text/plain
    const server = http2.createServer((req, res) => {
      res.setHeader('Content-Type', 'text/html; charset=utf-8');
      res.setHeader('X-Foo', 'bar');
      res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });
      res.end('ok');
    });
    

    Attempting to set a header field name or value that contains invalid characters will result in a TypeError being thrown.

    statusCode: number,
    statusMessage: string,
    ): this;

    Sends a response header to the request. The status code is a 3-digit HTTP status code, like 404. The last argument, headers, are the response headers.

    Returns a reference to the Http2ServerResponse, so that calls can be chained.

    For compatibility with HTTP/1, a human-readable statusMessage may be passed as the second argument. However, because the statusMessage has no meaning within HTTP/2, the argument will have no effect and a process warning will be emitted.

    const body = 'hello world';
    response.writeHead(200, {
      'Content-Length': Buffer.byteLength(body),
      'Content-Type': 'text/plain; charset=utf-8',
    });
    

    Content-Length is given in bytes not characters. TheBuffer.byteLength() API may be used to determine the number of bytes in a given encoding. On outbound messages, Node.js does not check if Content-Length and the length of the body being transmitted are equal or not. However, when receiving messages, Node.js will automatically reject messages when the Content-Length does not match the actual payload size.

    This method may be called at most one time on a message before response.end() is called.

    If response.write() or response.end() are called before calling this, the implicit/mutable headers will be calculated and call this function.

    When headers have been set with response.setHeader(), they will be merged with any headers passed to response.writeHead(), with the headers passed to response.writeHead() given precedence.

    // Returns content-type = text/plain
    const server = http2.createServer((req, res) => {
      res.setHeader('Content-Type', 'text/html; charset=utf-8');
      res.setHeader('X-Foo', 'bar');
      res.writeHead(200, { 'Content-Type': 'text/plain; charset=utf-8' });
      res.end('ok');
    });
    

    Attempting to set a header field name or value that contains invalid characters will result in a TypeError being thrown.

  • signal: AbortSignal,
    resource: (event: Event) => void
    ): Disposable;

    Listens once to the abort event on the provided signal.

    Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

    This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

    Returns a disposable so that it may be unsubscribed from more easily.

    import { addAbortListener } from 'node:events';
    
    function example(signal) {
      let disposable;
      try {
        signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
        disposable = addAbortListener(signal, (e) => {
          // Do something when signal is aborted.
        });
      } finally {
        disposable?.[Symbol.dispose]();
      }
    }
    
    @returns

    Disposable that removes the abort listener.

  • static fromWeb(
    writableStream: WritableStream,
    options?: Pick<WritableOptions<Writable>, 'signal' | 'decodeStrings' | 'highWaterMark' | 'objectMode'>

    A utility method for creating a Writable from a web WritableStream.

  • emitter: EventEmitter<DefaultEventMap> | EventTarget,
    name: string | symbol
    ): Function[];

    Returns a copy of the array of listeners for the event named eventName.

    For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

    For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

    import { getEventListeners, EventEmitter } from 'node:events';
    
    {
      const ee = new EventEmitter();
      const listener = () => console.log('Events are fun');
      ee.on('foo', listener);
      console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
    }
    {
      const et = new EventTarget();
      const listener = () => console.log('Events are fun');
      et.addEventListener('foo', listener);
      console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
    }
    
  • emitter: EventEmitter<DefaultEventMap> | EventTarget
    ): number;

    Returns the currently set max amount of listeners.

    For EventEmitters this behaves exactly the same as calling .getMaxListeners on the emitter.

    For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

    import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';
    
    {
      const ee = new EventEmitter();
      console.log(getMaxListeners(ee)); // 10
      setMaxListeners(11, ee);
      console.log(getMaxListeners(ee)); // 11
    }
    {
      const et = new EventTarget();
      console.log(getMaxListeners(et)); // 10
      setMaxListeners(11, et);
      console.log(getMaxListeners(et)); // 11
    }
    
  • static on(
    emitter: EventEmitter,
    eventName: string | symbol,
    options?: StaticEventEmitterIteratorOptions
    ): AsyncIterator<any[]>;
    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    // Emit later on
    process.nextTick(() => {
      ee.emit('foo', 'bar');
      ee.emit('foo', 42);
    });
    
    for await (const event of on(ee, 'foo')) {
      // The execution of this inner block is synchronous and it
      // processes one event at a time (even with await). Do not use
      // if concurrent execution is required.
      console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here
    

    Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

    An AbortSignal can be used to cancel waiting on events:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ac = new AbortController();
    
    (async () => {
      const ee = new EventEmitter();
    
      // Emit later on
      process.nextTick(() => {
        ee.emit('foo', 'bar');
        ee.emit('foo', 42);
      });
    
      for await (const event of on(ee, 'foo', { signal: ac.signal })) {
        // The execution of this inner block is synchronous and it
        // processes one event at a time (even with await). Do not use
        // if concurrent execution is required.
        console.log(event); // prints ['bar'] [42]
      }
      // Unreachable here
    })();
    
    process.nextTick(() => ac.abort());
    

    Use the close option to specify an array of event names that will end the iteration:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    // Emit later on
    process.nextTick(() => {
      ee.emit('foo', 'bar');
      ee.emit('foo', 42);
      ee.emit('close');
    });
    
    for await (const event of on(ee, 'foo', { close: ['close'] })) {
      console.log(event); // prints ['bar'] [42]
    }
    // the loop will exit after 'close' is emitted
    console.log('done'); // prints 'done'
    
    @returns

    An AsyncIterator that iterates eventName events emitted by the emitter

    static on(
    emitter: EventTarget,
    eventName: string,
    options?: StaticEventEmitterIteratorOptions
    ): AsyncIterator<any[]>;
    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    // Emit later on
    process.nextTick(() => {
      ee.emit('foo', 'bar');
      ee.emit('foo', 42);
    });
    
    for await (const event of on(ee, 'foo')) {
      // The execution of this inner block is synchronous and it
      // processes one event at a time (even with await). Do not use
      // if concurrent execution is required.
      console.log(event); // prints ['bar'] [42]
    }
    // Unreachable here
    

    Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

    An AbortSignal can be used to cancel waiting on events:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ac = new AbortController();
    
    (async () => {
      const ee = new EventEmitter();
    
      // Emit later on
      process.nextTick(() => {
        ee.emit('foo', 'bar');
        ee.emit('foo', 42);
      });
    
      for await (const event of on(ee, 'foo', { signal: ac.signal })) {
        // The execution of this inner block is synchronous and it
        // processes one event at a time (even with await). Do not use
        // if concurrent execution is required.
        console.log(event); // prints ['bar'] [42]
      }
      // Unreachable here
    })();
    
    process.nextTick(() => ac.abort());
    

    Use the close option to specify an array of event names that will end the iteration:

    import { on, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    // Emit later on
    process.nextTick(() => {
      ee.emit('foo', 'bar');
      ee.emit('foo', 42);
      ee.emit('close');
    });
    
    for await (const event of on(ee, 'foo', { close: ['close'] })) {
      console.log(event); // prints ['bar'] [42]
    }
    // the loop will exit after 'close' is emitted
    console.log('done'); // prints 'done'
    
    @returns

    An AsyncIterator that iterates eventName events emitted by the emitter

  • static once(
    emitter: EventEmitter,
    eventName: string | symbol,
    options?: StaticEventEmitterOptions
    ): Promise<any[]>;

    Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

    This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

    import { once, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    process.nextTick(() => {
      ee.emit('myevent', 42);
    });
    
    const [value] = await once(ee, 'myevent');
    console.log(value);
    
    const err = new Error('kaboom');
    process.nextTick(() => {
      ee.emit('error', err);
    });
    
    try {
      await once(ee, 'myevent');
    } catch (err) {
      console.error('error happened', err);
    }
    

    The special handling of the 'error' event is only used when events.once() is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

    import { EventEmitter, once } from 'node:events';
    
    const ee = new EventEmitter();
    
    once(ee, 'error')
      .then(([err]) => console.log('ok', err.message))
      .catch((err) => console.error('error', err.message));
    
    ee.emit('error', new Error('boom'));
    
    // Prints: ok boom
    

    An AbortSignal can be used to cancel waiting for the event:

    import { EventEmitter, once } from 'node:events';
    
    const ee = new EventEmitter();
    const ac = new AbortController();
    
    async function foo(emitter, event, signal) {
      try {
        await once(emitter, event, { signal });
        console.log('event emitted!');
      } catch (error) {
        if (error.name === 'AbortError') {
          console.error('Waiting for the event was canceled!');
        } else {
          console.error('There was an error', error.message);
        }
      }
    }
    
    foo(ee, 'foo', ac.signal);
    ac.abort(); // Abort waiting for the event
    ee.emit('foo'); // Prints: Waiting for the event was canceled!
    
    static once(
    emitter: EventTarget,
    eventName: string,
    options?: StaticEventEmitterOptions
    ): Promise<any[]>;

    Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

    This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

    import { once, EventEmitter } from 'node:events';
    import process from 'node:process';
    
    const ee = new EventEmitter();
    
    process.nextTick(() => {
      ee.emit('myevent', 42);
    });
    
    const [value] = await once(ee, 'myevent');
    console.log(value);
    
    const err = new Error('kaboom');
    process.nextTick(() => {
      ee.emit('error', err);
    });
    
    try {
      await once(ee, 'myevent');
    } catch (err) {
      console.error('error happened', err);
    }
    

    The special handling of the 'error' event is only used when events.once() is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

    import { EventEmitter, once } from 'node:events';
    
    const ee = new EventEmitter();
    
    once(ee, 'error')
      .then(([err]) => console.log('ok', err.message))
      .catch((err) => console.error('error', err.message));
    
    ee.emit('error', new Error('boom'));
    
    // Prints: ok boom
    

    An AbortSignal can be used to cancel waiting for the event:

    import { EventEmitter, once } from 'node:events';
    
    const ee = new EventEmitter();
    const ac = new AbortController();
    
    async function foo(emitter, event, signal) {
      try {
        await once(emitter, event, { signal });
        console.log('event emitted!');
      } catch (error) {
        if (error.name === 'AbortError') {
          console.error('Waiting for the event was canceled!');
        } else {
          console.error('There was an error', error.message);
        }
      }
    }
    
    foo(ee, 'foo', ac.signal);
    ac.abort(); // Abort waiting for the event
    ee.emit('foo'); // Prints: Waiting for the event was canceled!
    
  • n?: number,
    ...eventTargets: EventEmitter<DefaultEventMap> | EventTarget[]
    ): void;
    import { setMaxListeners, EventEmitter } from 'node:events';
    
    const target = new EventTarget();
    const emitter = new EventEmitter();
    
    setMaxListeners(5, target, emitter);
    
    @param n

    A non-negative number. The maximum number of listeners per EventTarget event.

    @param eventTargets

    Zero or more {EventTarget} or {EventEmitter} instances. If none are specified, n is set as the default max for all newly created {EventTarget} and {EventEmitter} objects.

  • static toWeb(
    streamWritable: Writable

    A utility method for creating a web WritableStream from a Writable.