This object is created internally by an HTTP server, not by the user. It is passed as the second parameter to the 'request'
event.
class
http2.Http2ServerResponse
class Http2ServerResponse<Request extends Http2ServerRequest = Http2ServerRequest>
- 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 anet.Socket
(ortls.TLSSocket
) but applies getters, setters, and methods based on HTTP/2 logic.destroyed
,readable
, andwritable
properties will be retrieved from and set onresponse.stream
.destroy
,emit
,end
,on
andonce
methods will be called onresponse.stream
.setTimeout
method will be called onresponse.stream.session
.pause
,read
,resume
, andwrite
will throw an error with codeERR_HTTP2_NO_SOCKET_MANIPULATION
. SeeHttp2Session 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 writable: boolean
Is
true
if it is safe to callwritable.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
afterwritable.end()
has been called. This property does not indicate whether the data has been flushed, for this usewritable.writableFinished
instead. - readonly writableHighWaterMark: number
Return the value of
highWaterMark
passed when creating thisWritable
. - 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'
. - static captureRejections: boolean
Value: boolean
Change the default
captureRejections
option on all newEventEmitter
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 individualEventEmitter
instances using theemitter.setMaxListeners(n)
method. To change the default for allEventEmitter
instances, theevents.defaultMaxListeners
property can be used. If this value is not a positive number, aRangeError
is thrown.Take caution when setting the
events.defaultMaxListeners
because the change affects allEventEmitter
instances, including those created before the change is made. However, callingemitter.setMaxListeners(n)
still has precedence overevents.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 singleEventEmitter
, theemitter.getMaxListeners()
andemitter.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 additionalemitter
,type
, andcount
properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Itsname
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. - event: 'close',listener: () => void): this;
Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: 'drain',listener: () => void): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: 'error',): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: 'finish',listener: () => void): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: 'pipe',): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: 'unpipe',): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
event: string | symbol,listener: (...args: any[]) => void): this;Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- 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'); });
- stream: ComposeFnParam | T | Iterable<T, any, any> | AsyncIterable<T, any, any>,): T;
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 untilwritable.uncork()
is called, which will pass them all towritable._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 ofwritable.cork()
without implementingwritable._writev()
may have an adverse effect on throughput.See also:
writable.uncork()
,writable._writev()
.- ): void;
Call
http2stream.pushStream()
with the given headers, and wrap the givenHttp2Stream
on a newly createdHttp2ServerResponse
as the callback parameter if successful. WhenHttp2ServerRequest
is closed, the callback is called with an errorERR_HTTP2_INVALID_STREAM
.@param headersAn object describing the headers
@param callbackCalled once
http2stream.pushStream()
is finished, or either when the attempt to create the pushedHttp2Stream
has failed or has been rejected, or the state ofHttp2ServerRequest
is closed prior to calling thehttp2stream.pushStream()
method - ): this;
Destroy the stream. Optionally emit an
'error'
event, and emit a'close'
event (unlessemitClose
is set tofalse
). After this call, the writable stream has ended and subsequent calls towrite()
orend()
will result in anERR_STREAM_DESTROYED
error. This is a destructive and immediate way to destroy a stream. Previous calls towrite()
may not have drained, and may trigger anERR_STREAM_DESTROYED
error. Useend()
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 errorOptional, an error to emit with
'error'
event. - emit(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
- end(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 callingresponse.write(data, encoding)
followed byresponse.end(callback)
.If
callback
is specified, it will be called when the response stream is finished.end(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 callingresponse.write(data, encoding)
followed byresponse.end(callback)
.If
callback
is specified, it will be called when the response stream is finished.end(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 callingresponse.write(data, encoding)
followed byresponse.end(callback)
.If
callback
is specified, it will be called when the response stream is finished. Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or
Symbol
s.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');
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 JavaScriptObject
. This means that typicalObject
methods such asobj.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'] }
Returns the current max listener value for the
EventEmitter
which is either set byemitter.setMaxListeners(n)
or defaults to EventEmitter.defaultMaxListeners.- name: string): boolean;
Returns
true
if the header identified byname
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
. Iflistener
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
- 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] ]
- eventName: string | symbol,listener: (...args: any[]) => void): this;
Alias for
emitter.removeListener()
. - on(event: 'close',listener: () => void): this;
Adds the
listener
function to the end of the listeners array for the event namedeventName
. No checks are made to see if thelistener
has already been added. Multiple calls passing the same combination ofeventName
andlistener
will result in thelistener
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 listenerThe callback function
- once(event: 'close',listener: () => void): this;
Adds a one-time
listener
function for the event namedeventName
. The next timeeventName
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 listenerThe callback function
- event: 'close',listener: () => void): this;
Adds the
listener
function to the beginning of the listeners array for the event namedeventName
. No checks are made to see if thelistener
has already been added. Multiple calls passing the same combination ofeventName
andlistener
will result in thelistener
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 listenerThe callback function
- event: 'close',listener: () => void): this;
Adds a one-time
listener
function for the event namedeventName
to the beginning of the listeners array. The next timeeventName
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 listenerThe callback function
- 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 namedeventName
.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 specifiedeventName
, thenremoveListener()
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()
orremoveAllListeners()
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 theonce('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. - encoding: BufferEncoding): this;
The
writable.setDefaultEncoding()
method sets the defaultencoding
for aWritable
stream.@param encodingThe 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 toresponse.writeHead()
, with the headers passed toresponse.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
EventEmitter
s will print a warning if more than10
listeners are added for a particular event. This is a useful default that helps finding memory leaks. Theemitter.setMaxListeners()
method allows the limit to be modified for this specificEventEmitter
instance. The value can be set toInfinity
(or0
) 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 tomsecs
. 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, thenHttp2Stream
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. The
writable.uncork()
method flushes all data buffered since cork was called.When using
writable.cork()
andwritable.uncork()
to manage the buffering of writes to a stream, defer calls towritable.uncork()
usingprocess.nextTick()
. Doing so allows batching of allwritable.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 towritable.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()
.- ): 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, the204
and304
responses must not include a message body.chunk
can be a string or a buffer. Ifchunk
is a string, the second parameter specifies how to encode it into a byte stream. By default theencoding
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 timeresponse.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. Returnsfalse
if all or part of the data was queued in user memory.'drain'
will be emitted when the buffer is free again.encoding: BufferEncoding,): 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, the204
and304
responses must not include a message body.chunk
can be a string or a buffer. Ifchunk
is a string, the second parameter specifies how to encode it into a byte stream. By default theencoding
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 timeresponse.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. Returnsfalse
if all or part of the data was queued in user memory.'drain'
will be emitted when the buffer is free again. Sends a status
100 Continue
to the client, indicating that the request body should be sent. See the'checkContinue'
event onHttp2Server
andHttp2SecureServer
.- 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. Thehints
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-readablestatusMessage
may be passed as the second argument. However, because thestatusMessage
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 theContent-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()
orresponse.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 toresponse.writeHead()
, with the headers passed toresponse.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-readablestatusMessage
may be passed as the second argument. However, because thestatusMessage
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 theContent-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()
orresponse.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 toresponse.writeHead()
, with the headers passed toresponse.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. - ): Disposable;
Listens once to the
abort
event on the providedsignal
.Listening to the
abort
event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can calle.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
AbortSignal
s in Node.js APIs by solving these two issues by listening to the event such thatstopImmediatePropagation
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](); } }
@returnsDisposable that removes the
abort
listener. - options?: Pick<WritableOptions<Writable>, 'signal' | 'decodeStrings' | 'highWaterMark' | 'objectMode'>
A utility method for creating a
Writable
from a webWritableStream
. - name: string | symbol): Function[];
Returns a copy of the array of listeners for the event named
eventName
.For
EventEmitter
s this behaves exactly the same as calling.listeners
on the emitter.For
EventTarget
s 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] ] }
- ): number;
Returns the currently set max amount of listeners.
For
EventEmitter
s this behaves exactly the same as calling.getMaxListeners
on the emitter.For
EventTarget
s 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 }
- 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 iterateseventName
events. It will throw if theEventEmitter
emits'error'
. It removes all listeners when exiting the loop. Thevalue
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'
@returnsAn
AsyncIterator
that iterateseventName
events emitted by theemitter
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 iterateseventName
events. It will throw if theEventEmitter
emits'error'
. It removes all listeners when exiting the loop. Thevalue
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'
@returnsAn
AsyncIterator
that iterateseventName
events emitted by theemitter
- emitter: EventEmitter,eventName: string | symbol,options?: StaticEventEmitterOptions): Promise<any[]>;
Creates a
Promise
that is fulfilled when theEventEmitter
emits the given event or that is rejected if theEventEmitter
emits'error'
while waiting. ThePromise
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 whenevents.once()
is used to wait for another event. Ifevents.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!
eventName: string,options?: StaticEventEmitterOptions): Promise<any[]>;Creates a
Promise
that is fulfilled when theEventEmitter
emits the given event or that is rejected if theEventEmitter
emits'error'
while waiting. ThePromise
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 whenevents.once()
is used to wait for another event. Ifevents.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,): void;
import { setMaxListeners, EventEmitter } from 'node:events'; const target = new EventTarget(); const emitter = new EventEmitter(); setMaxListeners(5, target, emitter);
@param nA non-negative number. The maximum number of listeners per
EventTarget
event.@param eventTargetsZero 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. A utility method for creating a web
WritableStream
from aWritable
.