Is true after 'close' has been emitted.
The message.complete property will be true if a complete HTTP message has
been received and successfully parsed.
This property is particularly useful as a means of determining if a client or server fully transmitted a message before a connection was terminated:
const req = http.request({
host: '127.0.0.1',
port: 8080,
method: 'POST'
}, (res) => {
res.resume();
res.on('end', () => {
if (!res.complete)
console.error(
'The connection was terminated while the message was still being sent');
});
});
Alias for message.socket.
Is true after readable.destroy() has been called.
Returns error if the stream has been destroyed with an error.
The request/response headers object.
Key-value pairs of header names and values. Header names are lower-cased.
// Prints something like:
//
// { 'user-agent': 'curl/7.22.0',
// host: '127.0.0.1:8000',
// accept: '*' }
console.log(request.getHeaders());
Duplicates in raw headers are handled in the following ways, depending on the header name:
age, authorization, content-length, content-type, etag, expires, from, host, if-modified-since, if-unmodified-since, last-modified, location,
max-forwards, proxy-authorization, referer, retry-after, server, or user-agent are discarded.set-cookie is always an array. Duplicates are added to the array.cookie headers, the values are joined together with '; '.Similar to message.headers, but there is no join logic and the values are always arrays of strings, even for headers received just once.
// Prints something like:
//
// { 'user-agent': ['curl/7.22.0'],
// host: ['127.0.0.1:8000'],
// accept: ['*'] }
console.log(request.headersDistinct);
In case of server request, the HTTP version sent by the client. In the case of
client response, the HTTP version of the connected-to server.
Probably either '1.1' or '1.0'.
Also message.httpVersionMajor is the first integer andmessage.httpVersionMinor is the second.
Only valid for request obtained from {@link Server}.
The request method as a string. Read only. Examples: 'GET', 'DELETE'.
The raw request/response headers list exactly as they were received.
The keys and values are in the same list. It is not a list of tuples. So, the even-numbered offsets are key values, and the odd-numbered offsets are the associated values.
Header names are not lowercased, and duplicates are not merged.
// Prints something like:
//
// [ 'user-agent',
// 'this is invalid because there can be only one',
// 'User-Agent',
// 'curl/7.22.0',
// 'Host',
// '127.0.0.1:8000',
// 'ACCEPT',
// '*' ]
console.log(request.rawHeaders);
The raw request/response trailer keys and values exactly as they were
received. Only populated at the 'end' event.
Is true if it is safe to call readable.read(), which means
the stream has not been destroyed or emitted 'error' or 'end'.
Returns whether the stream was destroyed or errored before emitting 'end'.
Returns whether 'data' has been emitted.
Getter for the property encoding of a given Readable stream. The encodingproperty can be set using the readable.setEncoding() method.
Becomes true when 'end' event is emitted.
This property reflects the current state of a Readable stream as described
in the Three states section.
Returns the value of highWaterMark passed when creating this Readable.
This property contains the number of bytes (or objects) in the queue
ready to be read. The value provides introspection data regarding
the status of the highWaterMark.
Getter for the property objectMode of a given Readable stream.
The net.Socket object associated with the connection.
With HTTPS support, use request.socket.getPeerCertificate() to obtain the
client's authentication details.
This property is guaranteed to be an instance of the net.Socket class,
a subclass of stream.Duplex, unless the user specified a socket
type other than net.Socket or internally nulled.
Only valid for response obtained from {@link ClientRequest}.
The 3-digit HTTP response status code. E.G. 404.
Only valid for response obtained from {@link ClientRequest}.
The HTTP response status message (reason phrase). E.G. OK or Internal Server Error.
The request/response trailers object. Only populated at the 'end' event.
Similar to message.trailers, but there is no join logic and the values are always arrays of strings, even for headers received just once.
Only populated at the 'end' event.
Only valid for request obtained from {@link Server}.
Request URL string. This contains only the URL that is present in the actual HTTP request. Take the following request:
GET /status?name=ryan HTTP/1.1
Accept: text/plain
To parse the URL into its parts:
new URL(request.url, `http://${request.getHeaders().host}`);
When request.url is '/status?name=ryan' and request.getHeaders().host is 'localhost:3000':
$ node
> new URL(request.url, `http://${request.getHeaders().host}`)
URL {
href: 'http://localhost:3000/status?name=ryan',
origin: 'http://localhost:3000',
protocol: 'http:',
username: '',
password: '',
host: 'localhost:3000',
hostname: 'localhost',
port: '3000',
pathname: '/status',
search: '?name=ryan',
searchParams: URLSearchParams { 'name' => 'ryan' },
hash: ''
}
Calls readable.destroy() with an AbortError and returns a promise that fulfills when the stream is finished.
Event emitter The defined events on documents including:
This method returns a new stream with chunks of the underlying stream paired with a counter
in the form [index, chunk]. The first index value is 0 and it increases by 1 for each chunk produced.
a stream of indexed pairs.
Calls destroy() on the socket that received the IncomingMessage. If erroris provided, an 'error' event is emitted on the socket and error is passed
as an argument to any listeners on the event.
This method returns a new stream with the first limit chunks dropped from the start.
the number of chunks to drop from the readable.
a stream with limit chunks dropped from the start.
Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbols.
const EventEmitter = require('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) ]
This method is similar to Array.prototype.every and calls fn on each chunk in the stream
to check if all awaited return values are truthy value for fn. Once an fn call on a chunk
awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false.
If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.
a function to call on each chunk of the stream. Async or not.
a promise evaluating to true if fn returned a truthy value for every one of the chunks.
This method allows filtering the stream. For each chunk in the stream the fn function will be called
and if it returns a truthy value, the chunk will be passed to the result stream.
If the fn function returns a promise - that promise will be awaited.
a function to filter chunks from the stream. Async or not.
a stream filtered with the predicate fn.
This method is similar to Array.prototype.find and calls fn on each chunk in the stream
to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy,
the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value.
If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.
a function to call on each chunk of the stream. Async or not.
a promise evaluating to the first chunk for which fn evaluated with a truthy value,
or undefined if no element was found.
This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.
It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.
a function to map over every chunk in the stream. May be async. May be a stream or generator.
a stream flat-mapped with the function fn.
This method allows iterating a stream. For each chunk in the stream the fn function will be called.
If the fn function returns a promise - that promise will be awaited.
This method is different from for await...of loops in that it can optionally process chunks concurrently.
In addition, a forEach iteration can only be stopped by having passed a signal option
and aborting the related AbortController while for await...of can be stopped with break or return.
In either case the stream will be destroyed.
This method is different from listening to the 'data' event in that it uses the readable event
in the underlying machinary and can limit the number of concurrent fn calls.
a function to call on each chunk of the stream. Async or not.
a promise for when the stream has finished.
Returns the current max listener value for the EventEmitter which is either
set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners}.
The readable.isPaused() method returns the current operating state of theReadable. This is used primarily by the mechanism that underlies thereadable.pipe() method. In most
typical cases, there will be no reason to
use this method directly.
const readable = new stream.Readable();
readable.isPaused(); // === false
readable.pause();
readable.isPaused(); // === true
readable.resume();
readable.isPaused(); // === false
The iterator created by this method gives users the option to cancel the destruction
of the stream if the for await...of loop is exited by return, break, or throw,
or if the iterator should destroy the stream if the stream emitted an error during iteration.
When set to false, calling return on the async iterator,
or exiting a for await...of iteration using a break, return, or throw will not destroy the stream.
Default: true.
Returns the number of listeners listening to 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.
The name of the event being listened for
The event handler 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] ]
This method allows mapping over the stream. The fn function will be called for every chunk in the stream.
If the fn function returns a promise - that promise will be awaited before being passed to the result stream.
a function to map over every chunk in the stream. Async or not.
a stream mapped with the function fn.
Alias for emitter.removeListener().
The readable.pause() method will cause a stream in flowing mode to stop
emitting 'data' events, switching out of flowing mode. Any data that
becomes available will remain in the internal buffer.
const readable = getReadableStreamSomehow();
readable.on('data', (chunk) => {
console.log(`Received ${chunk.length} bytes of data.`);
readable.pause();
console.log('There will be no additional data for 1 second.');
setTimeout(() => {
console.log('Now data will start flowing again.');
readable.resume();
}, 1000);
});
The readable.pause() method has no effect if there is a 'readable'event listener.
Returns a copy of the array of listeners for the event named eventName,
including any wrappers (such as those created by .once()).
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');
The readable.read() method reads data out of the internal buffer and
returns it. If no data is available to be read, null is returned. By default,
the data is returned as a Buffer object unless an encoding has been
specified using the readable.setEncoding() method or the stream is operating
in object mode.
The optional size argument specifies a specific number of bytes to read. Ifsize bytes are not available to be read, null will be returned _unless_the stream has ended, in which
case all of the data remaining in the internal
buffer will be returned.
If the size argument is not specified, all of the data contained in the
internal buffer will be returned.
The size argument must be less than or equal to 1 GiB.
The readable.read() method should only be called on Readable streams
operating in paused mode. In flowing mode, readable.read() is called
automatically until the internal buffer is fully drained.
const readable = getReadableStreamSomehow();
// 'readable' may be triggered multiple times as data is buffered in
readable.on('readable', () => {
let chunk;
console.log('Stream is readable (new data received in buffer)');
// Use a loop to make sure we read all currently available data
while (null !== (chunk = readable.read())) {
console.log(`Read ${chunk.length} bytes of data...`);
}
});
// 'end' will be triggered once when there is no more data available
readable.on('end', () => {
console.log('Reached end of stream.');
});
Each call to readable.read() returns a chunk of data, or null. The chunks
are not concatenated. A while loop is necessary to consume all data
currently in the buffer. When reading a large file .read() may return null,
having consumed all buffered content so far, but there is still more data to
come not yet buffered. In this case a new 'readable' event will be emitted
when there is more data in the buffer. Finally the 'end' event will be
emitted when there is no more data to come.
Therefore to read a file's whole contents from a readable, it is necessary
to collect chunks across multiple 'readable' events:
const chunks = [];
readable.on('readable', () => {
let chunk;
while (null !== (chunk = readable.read())) {
chunks.push(chunk);
}
});
readable.on('end', () => {
const content = chunks.join('');
});
A Readable stream in object mode will always return a single item from
a call to readable.read(size), regardless of the value of thesize argument.
If the readable.read() method returns a chunk of data, a 'data' event will
also be emitted.
Calling read after the 'end' event has
been emitted will return null. No runtime error will be raised.
Optional argument to specify how much data to read.
This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.
If no initial value is supplied the first chunk of the stream is used as the initial value.
If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.
The reducer function iterates the stream element-by-element which means that there is no concurrency parameter
or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.
a reducer function to call over every chunk in the stream. Async or not.
the initial value to use in the reduction.
a promise for the final value of the reduction.
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.
The readable.resume() method causes an explicitly paused Readable stream to
resume emitting 'data' events, switching the stream into flowing mode.
The readable.resume() method can be used to fully consume the data from a
stream without actually processing any of that data:
getReadableStreamSomehow()
.resume()
.on('end', () => {
console.log('Reached the end, but did not read anything.');
});
The readable.resume() method has no effect if there is a 'readable'event listener.
The readable.setEncoding() method sets the character encoding for
data read from the Readable stream.
By default, no encoding is assigned and stream data will be returned asBuffer objects. Setting an encoding causes the stream data
to be returned as strings of the specified encoding rather than as Bufferobjects. For instance, calling readable.setEncoding('utf8') will cause the
output data to be interpreted as UTF-8 data, and passed as strings. Callingreadable.setEncoding('hex') will cause the data to be encoded in hexadecimal
string format.
The Readable stream will properly handle multi-byte characters delivered
through the stream that would otherwise become improperly decoded if simply
pulled from the stream as Buffer objects.
const readable = getReadableStreamSomehow();
readable.setEncoding('utf8');
readable.on('data', (chunk) => {
assert.equal(typeof chunk, 'string');
console.log('Got %d characters of string data:', chunk.length);
});
The encoding to use.
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 toInfinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
Calls message.socket.setTimeout(msecs, callback).
This method is similar to Array.prototype.some and calls fn on each chunk in the stream
until the awaited return value is true (or any truthy value). Once an fn call on a chunk
awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true.
If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.
a function to call on each chunk of the stream. Async or not.
a promise evaluating to true if fn returned a truthy value for at least one of the chunks.
This method returns a new stream with the first limit chunks.
the number of chunks to take from the readable.
a stream with limit chunks taken.
This method allows easily obtaining the contents of a stream.
As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.
a promise containing an array with the contents of the stream.
The readable.unpipe() method detaches a Writable stream previously attached
using the pipe method.
If the destination is not specified, then all pipes are detached.
If the destination is specified, but no pipe is set up for it, then
the method does nothing.
const fs = require('fs');
const readable = getReadableStreamSomehow();
const writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',
// but only for the first second.
readable.pipe(writable);
setTimeout(() => {
console.log('Stop writing to file.txt.');
readable.unpipe(writable);
console.log('Manually close the file stream.');
writable.end();
}, 1000);
Optional specific stream to unpipe
Passing chunk as null signals the end of the stream (EOF) and behaves the
same as readable.push(null), after which no more data can be written. The EOF
signal is put at the end of the buffer and any buffered data will still be
flushed.
The readable.unshift() method pushes a chunk of data back into the internal
buffer. This is useful in certain situations where a stream is being consumed by
code that needs to "un-consume" some amount of data that it has optimistically
pulled out of the source, so that the data can be passed on to some other party.
The stream.unshift(chunk) method cannot be called after the 'end' event
has been emitted or a runtime error will be thrown.
Developers using stream.unshift() often should consider switching to
use of a Transform stream instead. See the API for stream implementers section for more information.
// Pull off a header delimited by \n\n.
// Use unshift() if we get too much.
// Call the callback with (error, header, stream).
const { StringDecoder } = require('string_decoder');
function parseHeader(stream, callback) {
stream.on('error', callback);
stream.on('readable', onReadable);
const decoder = new StringDecoder('utf8');
let header = '';
function onReadable() {
let chunk;
while (null !== (chunk = stream.read())) {
const str = decoder.write(chunk);
if (str.includes('\n\n')) {
// Found the header boundary.
const split = str.split(/\n\n/);
header += split.shift();
const remaining = split.join('\n\n');
const buf = Buffer.from(remaining, 'utf8');
stream.removeListener('error', callback);
// Remove the 'readable' listener before unshifting.
stream.removeListener('readable', onReadable);
if (buf.length)
stream.unshift(buf);
// Now the body of the message can be read from the stream.
callback(null, header, stream);
return;
}
// Still reading the header.
header += str;
}
}
}
Unlike push, stream.unshift(chunk) will not
end the reading process by resetting the internal reading state of the stream.
This can cause unexpected results if readable.unshift() is called during a
read (i.e. from within a _read implementation on a
custom stream). Following the call to readable.unshift() with an immediate push will reset the reading state appropriately,
however it is best to simply avoid calling readable.unshift() while in the
process of performing a read.
Chunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a string, Buffer, Uint8Array or null. For object mode
streams, chunk may be any JavaScript value.
Encoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.
Prior to Node.js 0.10, streams did not implement the entire stream module API
as it is currently defined. (See Compatibility for more information.)
When using an older Node.js library that emits 'data' events and has a pause method that is advisory only, thereadable.wrap() method can be used to create a Readable
stream that uses
the old stream as its data source.
It will rarely be necessary to use readable.wrap() but the method has been
provided as a convenience for interacting with older Node.js applications and
libraries.
const { OldReader } = require('./old-api-module.js');
const { Readable } = require('stream');
const oreader = new OldReader();
const myReader = new Readable().wrap(oreader);
myReader.on('readable', () => {
myReader.read(); // etc.
});
An "old style" readable stream
Generated using TypeDoc
The
message.abortedproperty will betrueif the request has been aborted.v10.1.0
Since v17.0.0,v16.12.0 - Check
message.destroyedfrom stream.Readable.