Class: LogToEvTransport
Extends
TransportStream
Constructors
new LogToEvTransport()
new LogToEvTransport(
opts
?):LogToEvTransport
Parameters
• opts?: any
Returns
Overrides
TransportStream.constructor
Properties
closed
readonly
closed:boolean
Is true after 'close' has been emitted.
Since
v8.0.0
Inherited from
TransportStream.closed
destroyed
destroyed:
boolean
Is true
after writable.destroy()
has been called.
Since
v8.0.0
Inherited from
TransportStream.destroyed
errored
readonly
errored:Error
Returns error if the stream has been destroyed with an error.
Since
v18.0.0
Inherited from
TransportStream.errored
format?
optional
format:Format
Inherited from
TransportStream.format
handleExceptions?
optional
handleExceptions:boolean
Inherited from
TransportStream.handleExceptions
handleRejections?
optional
handleRejections:boolean
Inherited from
TransportStream.handleRejections
level?
optional
level:string
Inherited from
TransportStream.level
silent?
optional
silent:boolean
Inherited from
TransportStream.silent
writable
readonly
writable:boolean
Is true
if it is safe to call writable.write()
, which means
the stream has not been destroyed, errored or ended.
Since
v11.4.0
Inherited from
TransportStream.writable
writableCorked
readonly
writableCorked:number
Number of times writable.uncork()
needs to be
called in order to fully uncork the stream.
Since
v13.2.0, v12.16.0
Inherited from
TransportStream.writableCorked
writableEnded
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.
Since
v12.9.0
Inherited from
TransportStream.writableEnded
writableFinished
readonly
writableFinished:boolean
Is set to true
immediately before the 'finish'
event is emitted.
Since
v12.6.0
Inherited from
TransportStream.writableFinished
writableHighWaterMark
readonly
writableHighWaterMark:number
Return the value of highWaterMark
passed when creating this Writable
.
Since
v9.3.0
Inherited from
TransportStream.writableHighWaterMark
writableLength
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
.
Since
v9.4.0
Inherited from
TransportStream.writableLength
writableNeedDrain
readonly
writableNeedDrain:boolean
Is true
if the stream's buffer has been full and stream will emit 'drain'.
Since
v15.2.0, v14.17.0
Inherited from
TransportStream.writableNeedDrain
writableObjectMode
readonly
writableObjectMode:boolean
Getter for the property objectMode
of a given Writable
stream.
Since
v12.3.0
Inherited from
TransportStream.writableObjectMode
captureRejectionSymbol
readonly
static
captureRejectionSymbol: typeofcaptureRejectionSymbol
Inherited from
TransportStream.captureRejectionSymbol
captureRejections
static
captureRejections:boolean
Sets or gets the default captureRejection value for all emitters.
Inherited from
TransportStream.captureRejections
defaultMaxListeners
static
defaultMaxListeners:number
Inherited from
TransportStream.defaultMaxListeners
errorMonitor
readonly
static
errorMonitor: typeoferrorMonitor
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.
Inherited from
TransportStream.errorMonitor
Methods
_construct()?
optional
_construct(callback
):void
Parameters
• callback
Returns
void
Inherited from
TransportStream._construct
_destroy()
_destroy(
error
,callback
):void
Parameters
• error: Error
• callback
Returns
void
Inherited from
TransportStream._destroy
_final()
_final(
callback
):void
Parameters
• callback
Returns
void
Inherited from
TransportStream._final
_write()
_write(
chunk
,encoding
,callback
):void
Parameters
• chunk: any
• encoding: BufferEncoding
• callback
Returns
void
Inherited from
TransportStream._write
_writev()?
optional
_writev(chunks
,callback
):void
Parameters
• chunks: object
[]
• callback
Returns
void
Inherited from
TransportStream._writev
addListener()
addListener(event, listener)
addListener(
event
,listener
):this
Event emitter The defined events on documents including:
- close
- drain
- error
- finish
- pipe
- unpipe
Parameters
• event: "close"
• listener
Returns
this
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: "drain"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: "error"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: "finish"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: "pipe"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: "unpipe"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
addListener(event, listener)
addListener(
event
,listener
):this
Alias for emitter.on(eventName, listener)
.
Parameters
• event: string
| symbol
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.addListener
close()?
optional
close():void
Returns
void
Inherited from
TransportStream.close
cork()
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 implementingwritable._writev()
may have an adverse effect on throughput.
See also: writable.uncork()
, writable._writev()
.
Returns
void
Since
v0.11.2
Inherited from
TransportStream.cork
destroy()
destroy(
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 towrite()
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()
.
Parameters
• error?: Error
Optional, an error to emit with 'error'
event.
Returns
this
Since
v8.0.0
Inherited from
TransportStream.destroy
emit()
emit(event)
emit(
event
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "close"
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event)
emit(
event
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "drain"
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event, err)
emit(
event
,err
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "error"
• err: Error
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event)
emit(
event
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "finish"
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event, src)
emit(
event
,src
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "pipe"
• src: Readable
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event, src)
emit(
event
,src
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: "unpipe"
• src: Readable
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
emit(event, args)
emit(
event
, ...args
):boolean
Synchronously calls each of the listeners registered for the event namedeventName
, in the order they were registered, passing the supplied arguments
to each.
Returns true
if the event had listeners, false
otherwise.
const EventEmitter = require('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
Parameters
• event: string
| symbol
• ...args: any
[]
Returns
boolean
Since
v0.1.26
Inherited from
TransportStream.emit
end()
end(cb)
end(
cb
?):this
Calling the writable.end()
method signals that no more data will be written
to the Writable
. The optional chunk
and encoding
arguments allow one
final additional chunk of data to be written immediately before closing the
stream.
Calling the write method after calling end will raise an error.
// Write 'hello, ' and then end with 'world!'.
const fs = require('fs');
const file = fs.createWriteStream('example.txt');
file.write('hello, ');
file.end('world!');
// Writing more now is not allowed!
Parameters
• cb?
Returns
this
Since
v0.9.4
Inherited from
TransportStream.end
end(chunk, cb)
end(
chunk
,cb
?):this
Parameters
• chunk: any
• cb?
Returns
this
Inherited from
TransportStream.end
end(chunk, encoding, cb)
end(
chunk
,encoding
,cb
?):this
Parameters
• chunk: any
• encoding: BufferEncoding
• cb?
Returns
this
Inherited from
TransportStream.end
eventNames()
eventNames(): (
string
|symbol
)[]
Returns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbol
s.
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) ]
Returns
(string
| symbol
)[]
Since
v6.0.0
Inherited from
TransportStream.eventNames
getMaxListeners()
getMaxListeners():
number
Returns the current max listener value for the EventEmitter
which is either
set by emitter.setMaxListeners(n)
or defaults to defaultMaxListeners.
Returns
number
Since
v1.0.0
Inherited from
TransportStream.getMaxListeners
listenerCount()
listenerCount(
eventName
):number
Returns the number of listeners listening to the event named eventName
.
Parameters
• eventName: string
| symbol
The name of the event being listened for
Returns
number
Since
v3.2.0
Inherited from
TransportStream.listenerCount
listeners()
listeners(
eventName
):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] ]
Parameters
• eventName: string
| symbol
Returns
Function
[]
Since
v0.1.26
Inherited from
TransportStream.listeners
log()
log(
info
,callback
):any
Parameters
• info: any
• callback: any
Returns
any
Overrides
TransportStream.log
logv()?
optional
logv(info
,next
):any
Parameters
• info: any
• next
Returns
any
Inherited from
TransportStream.logv
off()
off(
eventName
,listener
):this
Alias for emitter.removeListener()
.
Parameters
• eventName: string
| symbol
• listener
Returns
this
Since
v10.0.0
Inherited from
TransportStream.off
on()
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "close"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "drain"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "error"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "finish"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "pipe"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "unpipe"
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
on(event, listener)
on(
event
,listener
):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. Theemitter.prependListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: string
| symbol
• listener
The callback function
Returns
this
Since
v0.1.101
Inherited from
TransportStream.on
once()
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "close"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "drain"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "error"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "finish"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "pipe"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: "unpipe"
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
once(event, listener)
once(
event
,listener
):this
Adds a one-timelistener
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. Theemitter.prependOnceListener()
method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
Parameters
• event: string
| symbol
• listener
The callback function
Returns
this
Since
v0.3.0
Inherited from
TransportStream.once
pipe()
pipe<
T
>(destination
,options
?):T
Type Parameters
• T extends WritableStream
Parameters
• destination: T
• options?
• options.end?: boolean
Returns
T
Inherited from
TransportStream.pipe
prependListener()
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "close"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "drain"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "error"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "finish"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "pipe"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: "unpipe"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependListener(event, listener)
prependListener(
event
,listener
):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.
Parameters
• event: string
| symbol
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependListener
prependOnceListener()
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "close"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "drain"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "error"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "finish"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "pipe"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: "unpipe"
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
prependOnceListener(event, listener)
prependOnceListener(
event
,listener
):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.
Parameters
• event: string
| symbol
• listener
The callback function
Returns
this
Since
v6.0.0
Inherited from
TransportStream.prependOnceListener
rawListeners()
rawListeners(
eventName
):Function
[]
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');
Parameters
• eventName: string
| symbol
Returns
Function
[]
Since
v9.4.0
Inherited from
TransportStream.rawListeners
removeAllListeners()
removeAllListeners(
event
?):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.
Parameters
• event?: string
| symbol
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeAllListeners
removeListener()
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "close"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "drain"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "error"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "finish"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "pipe"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: "unpipe"
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
removeListener(event, listener)
removeListener(
event
,listener
):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 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 anyremoveListener()
or removeAllListeners()
calls after emitting and before the last listener finishes execution
will not remove them fromemit()
in progress. Subsequent events behave as expected.
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:
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.
Parameters
• event: string
| symbol
• listener
Returns
this
Since
v0.1.26
Inherited from
TransportStream.removeListener
setDefaultEncoding()
setDefaultEncoding(
encoding
):this
The writable.setDefaultEncoding()
method sets the default encoding
for a Writable
stream.
Parameters
• encoding: BufferEncoding
The new default encoding
Returns
this
Since
v0.11.15
Inherited from
TransportStream.setDefaultEncoding
setMaxListeners()
setMaxListeners(
n
):this
By default EventEmitter
s 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.
Parameters
• n: number
Returns
this
Since
v0.3.5
Inherited from
TransportStream.setMaxListeners
uncork()
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()
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 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()
.
Returns
void
Since
v0.11.2
Inherited from
TransportStream.uncork
write()
write(chunk, callback)
write(
chunk
,callback
?):boolean
The writable.write()
method writes some data to the stream, and calls the
supplied callback
once the data has been fully handled. If an error
occurs, the callback
will be called with the error as its
first argument. The callback
is called asynchronously and before 'error'
is
emitted.
The return value is true
if the internal buffer is less than thehighWaterMark
configured when the stream was created after admitting chunk
.
If false
is returned, further attempts to write data to the stream should
stop until the 'drain'
event is emitted.
While a stream is not draining, calls to write()
will buffer chunk
, and
return false. Once all currently buffered chunks are drained (accepted for
delivery by the operating system), the 'drain'
event will be emitted.
Once write()
returns false, do not write more chunks
until the 'drain'
event is emitted. While calling write()
on a stream that
is not draining is allowed, Node.js will buffer all written chunks until
maximum memory usage occurs, at which point it will abort unconditionally.
Even before it aborts, high memory usage will cause poor garbage collector
performance and high RSS (which is not typically released back to the system,
even after the memory is no longer required). Since TCP sockets may never
drain if the remote peer does not read the data, writing a socket that is
not draining may lead to a remotely exploitable vulnerability.
Writing data while the stream is not draining is particularly
problematic for a Transform
, because the Transform
streams are paused
by default until they are piped or a 'data'
or 'readable'
event handler
is added.
If the data to be written can be generated or fetched on demand, it is
recommended to encapsulate the logic into a Readable
and use pipe. However, if calling write()
is preferred, it is
possible to respect backpressure and avoid memory issues using the 'drain'
event:
function write(data, cb) {
if (!stream.write(data)) {
stream.once('drain', cb);
} else {
process.nextTick(cb);
}
}
// Wait for cb to be called before doing any other write.
write('hello', () => {
console.log('Write completed, do more writes now.');
});
A Writable
stream in object mode will always ignore the encoding
argument.
Parameters
• chunk: any
Optional data to write. For streams not operating in object mode, chunk
must be a string, Buffer
or Uint8Array
. For object mode streams, chunk
may be any
JavaScript value other than null
.
• callback?
Callback for when this chunk of data is flushed.
Returns
boolean
false
if the stream wishes for the calling code to wait for the 'drain'
event to be emitted before continuing to write additional data; otherwise true
.
Since
v0.9.4
Inherited from
TransportStream.write
write(chunk, encoding, callback)
write(
chunk
,encoding
,callback
?):boolean
Parameters
• chunk: any
• encoding: BufferEncoding
• callback?
Returns
boolean
Inherited from
TransportStream.write
fromWeb()
static
fromWeb(writableStream
,options
?):Writable
Experimental
A utility method for creating a Writable
from a web WritableStream
.
Parameters
• writableStream: WritableStream
<any
>
• options?: Pick
<WritableOptions
, "signal"
| "decodeStrings"
| "highWaterMark"
| "objectMode"
>
Returns
Writable
Since
v17.0.0
Inherited from
TransportStream.fromWeb
getEventListeners()
static
getEventListeners(emitter
,name
):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.
const { getEventListeners, EventEmitter } = require('events');
{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
getEventListeners(ee, 'foo'); // [listener]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
getEventListeners(et, 'foo'); // [listener]
}
Parameters
• emitter: EventEmitter
| DOMEventTarget
• name: string
| symbol
Returns
Function
[]
Since
v15.2.0, v14.17.0
Inherited from
TransportStream.getEventListeners
listenerCount()
static
listenerCount(emitter
,eventName
):number
A class method that returns the number of listeners for the given eventName
registered on the given emitter
.
const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2
Parameters
• emitter: EventEmitter
The emitter to query
• eventName: string
| symbol
The event name
Returns
number
Since
v0.9.12
Deprecated
Since v3.2.0 - Use listenerCount
instead.
Inherited from
TransportStream.listenerCount
on()
static
on(emitter
,eventName
,options
?):AsyncIterableIterator
<any
>
const { on, EventEmitter } = require('events');
(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')) {
// 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:
const { on, EventEmitter } = require('events');
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());
Parameters
• emitter: EventEmitter
• eventName: string
The name of the event being listened for
• options?: StaticEventEmitterOptions
Returns
AsyncIterableIterator
<any
>
that iterates eventName
events emitted by the emitter
Since
v13.6.0, v12.16.0
Inherited from
TransportStream.on
once()
once(emitter, eventName, options)
static
once(emitter
,eventName
,options
?):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.
const { once, EventEmitter } = require('events');
async function run() {
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.log('error happened', err);
}
}
run();
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:
const { EventEmitter, once } = require('events');
const ee = new EventEmitter();
once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.log('error', err.message));
ee.emit('error', new Error('boom'));
// Prints: ok boom
An AbortSignal
can be used to cancel waiting for the event:
const { EventEmitter, once } = require('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!
Parameters
• emitter: NodeEventTarget
• eventName: string
| symbol
• options?: StaticEventEmitterOptions
Returns
Promise
<any
[]>
Since
v11.13.0, v10.16.0
Inherited from
TransportStream.once
once(emitter, eventName, options)
static
once(emitter
,eventName
,options
?):Promise
<any
[]>
Parameters
• emitter: DOMEventTarget
• eventName: string
• options?: StaticEventEmitterOptions
Returns
Promise
<any
[]>
Inherited from
TransportStream.once
setMaxListeners()
static
setMaxListeners(n
?, ...eventTargets
?):void
const {
setMaxListeners,
EventEmitter
} = require('events');
const target = new EventTarget();
const emitter = new EventEmitter();
setMaxListeners(5, target, emitter);
Parameters
• n?: number
A non-negative number. The maximum number of listeners per EventTarget
event.
• ...eventTargets?: (EventEmitter
| DOMEventTarget
)[]
Returns
void
Since
v15.4.0
Inherited from
TransportStream.setMaxListeners
toWeb()
static
toWeb(streamWritable
):WritableStream
<any
>
Experimental
A utility method for creating a web WritableStream
from a Writable
.
Parameters
• streamWritable: Writable
Returns
WritableStream
<any
>
Since
v17.0.0
Inherited from
TransportStream.toWeb