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Class: Collector

Abstract class for defining a new Collector.

Abstract​

Extends​

  • EventEmitter

Extended by​

Constructors​

new Collector()​

new Collector(filter, options): Collector

Parameters​

• filter: CollectorFilter<any>

• options: CollectorOptions = {}

Returns​

Collector

Overrides​

EventEmitter.constructor

Properties​

_idletimeout​

protected _idletimeout: Timeout

_timeout​

protected _timeout: Timeout

collected​

collected: Collection<string, any>

ended​

ended: boolean

filter()​

filter: (...args) => boolean | Promise<boolean>

Parameters​

• ...args: any[]

Returns​

boolean | Promise<boolean>

options​

options: CollectorOptions

captureRejectionSymbol​

readonly static captureRejectionSymbol: typeof captureRejectionSymbol

Inherited from​

EventEmitter.captureRejectionSymbol

captureRejections​

static captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Inherited from​

EventEmitter.captureRejections

defaultMaxListeners​

static defaultMaxListeners: number

Inherited from​

EventEmitter.defaultMaxListeners

errorMonitor​

readonly static errorMonitor: typeof errorMonitor

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

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

Inherited from​

EventEmitter.errorMonitor

Accessors​

next​

get next(): Promise<any>

Returns a promise that resolves with the next collected element; rejects with collected elements if the collector finishes without receiving a next element

Returns​

Promise<any>

Methods​

[asyncIterator]()​

[asyncIterator](): any

Allows collectors to be consumed with for-await-of loops

Returns​

any

See​

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of

addListener()​

addListener(eventName, listener): this

Alias for emitter.on(eventName, listener).

Parameters​

• eventName: string | symbol

• listener

Returns​

this

Since​

v0.1.26

Inherited from​

EventEmitter.addListener

checkEnd()​

checkEnd(): void

Checks whether the collector should end, and if so, ends it.

Returns​

void

clearImmediate()​

clearImmediate(immediate): void

Clears an immediate.

Parameters​

• immediate: Immediate

Immediate to cancel

Returns​

void

clearInterval()​

clearInterval(interval): void

Clears an interval.

Parameters​

• interval: Timeout

Interval to cancel

Returns​

void

clearTimeout()​

clearTimeout(timeout): void

Clears a timeout.

Parameters​

• timeout: Timeout

Timeout to cancel

Returns​

void

collect()​

collect(...args): string | false

Handles incoming events from the handleCollect function. Returns null if the event should not be collected, or returns an object describing the data that should be stored.

Parameters​

• ...args: any[]

Returns​

string | false

the id if the object should be collected, if it shouldnt be collected then it will return null or false.

See​

Collector#handleCollect

Abstract​

destroy()​

destroy(): void

Destroys all assets used by the base client.

Returns​

void

dispose()​

dispose(...args): string

Handles incoming events from the handleDispose. Returns null if the event should not be disposed, or returns the key that should be removed.

Parameters​

• ...args: any[]

Any args the event listener emits

Returns​

string

Key to remove from the collection, if any

See​

Collector#handleDispose

Abstract​

emit()​

emit(eventName, ...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​

• eventName: string | symbol

• ...args: any[]

Returns​

boolean

Since​

v0.1.26

Inherited from​

EventEmitter.emit

endReason()​

endReason(...args): string

The reason this collector has ended or will end with.

Parameters​

• ...args: any[]

Returns​

string

Reason to end the collector, if any

Abstract​

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 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) ]

Returns​

(string | symbol)[]

Since​

v6.0.0

Inherited from​

EventEmitter.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​

EventEmitter.getMaxListeners

handleCollect()​

handleCollect(...args): Promise<void>

Call this to handle an event as a collectable element. Accepts any event data as parameters.

Parameters​

• ...args: any[]

The arguments emitted by the listener

Returns​

Promise<void>

Emits​

Collector#collect

handleDispose()​

handleDispose(...args): Promise<void>

Call this to remove an element from the collection. Accepts any event data as parameters.

Parameters​

• ...args: any[]

The arguments emitted by the listener

Returns​

Promise<void>

Emits​

Collector#dispose

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​

EventEmitter.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​

EventEmitter.listeners

off()​

off(eventName, listener): this

Alias for emitter.removeListener().

Parameters​

• eventName: string | symbol

• listener

Returns​

this

Since​

v10.0.0

Inherited from​

EventEmitter.off

on()​

on(eventName, 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 eventNameand 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​

• eventName: string | symbol

The name of the event.

• listener

The callback function

Returns​

this

Since​

v0.1.101

Inherited from​

EventEmitter.on

once()​

once(eventName, 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​

• eventName: string | symbol

The name of the event.

• listener

The callback function

Returns​

this

Since​

v0.3.0

Inherited from​

EventEmitter.once

prependListener()​

prependListener(eventName, 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 eventNameand 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​

• eventName: string | symbol

The name of the event.

• listener

The callback function

Returns​

this

Since​

v6.0.0

Inherited from​

EventEmitter.prependListener

prependOnceListener()​

prependOnceListener(eventName, 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​

• eventName: string | symbol

The name of the event.

• listener

The callback function

Returns​

this

Since​

v6.0.0

Inherited from​

EventEmitter.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​

EventEmitter.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​

EventEmitter.removeAllListeners

removeListener()​

removeListener(eventName, 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​

• eventName: string | symbol

• listener

Returns​

this

Since​

v0.1.26

Inherited from​

EventEmitter.removeListener

resetTimer()​

resetTimer(options?): void

Resets the collectors timeout and idle timer.

Parameters​

• options? = ...

Options

• options.idle?: any

How long to stop the collector after inactivity in milliseconds

• options.time?: any

How long to run the collector for in milliseconds

Returns​

void

setImmediate()​

setImmediate(fn, ...args): Immediate

Sets an immediate that will be automatically cancelled if the client is destroyed.

Parameters​

• fn

Function to execute

• ...args: any[]

Arguments for the function

Returns​

Immediate

setInterval()​

setInterval(fn, delay, ...args): Timeout

Sets an interval that will be automatically cancelled if the client is destroyed.

Parameters​

• fn

Function to execute

• delay: number

Time to wait between executions (in milliseconds)

• ...args: any[]

Arguments for the function

Returns​

Timeout

setMaxListeners()​

setMaxListeners(n): this

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set 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​

EventEmitter.setMaxListeners

setTimeout()​

setTimeout(fn, delay, ...args): Timeout

Sets a timeout that will be automatically cancelled if the client is destroyed.

Parameters​

• fn

Function to execute

• delay: number

Time to wait before executing (in milliseconds)

• ...args: any[]

Arguments for the function

Returns​

Timeout

stop()​

stop(reason?): void

Stops this collector and emits the end event.

Parameters​

• reason?: string = 'user'

The reason this collector is ending

Returns​

void

Emits​

Collector#end

getEventListeners()​

static getEventListeners(emitter, name): Function[]

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

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

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

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​

EventEmitter.getEventListeners

listenerCount()​

static listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered 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​

EventEmitter.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​

EventEmitter.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​

EventEmitter.once

once(emitter, eventName, options)​

static once(emitter, eventName, options?): Promise<any[]>

Parameters​

• emitter: DOMEventTarget

• eventName: string

• options?: StaticEventEmitterOptions

Returns​

Promise<any[]>

Inherited from​

EventEmitter.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​

EventEmitter.setMaxListeners