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Class CallbackSourceNode<Out>

Type parameters

Hierarchy

Index

Constructors

constructor

Properties

callback

callback: (options?: PullOptions) => Out | Promise<Out>

Type declaration

    • Parameters

      Returns Out | Promise<Out>

Protected options

Node options

Static Readonly captureRejectionSymbol

captureRejectionSymbol: typeof captureRejectionSymbol

Static captureRejections

captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

Static defaultMaxListeners

defaultMaxListeners: number

Static Readonly errorMonitor

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.

Accessors

model

  • get model(): Model<any, any>
  • Graph this model is part of

    Returns Model<any, any>

    Positioning model

Protected source

Methods

addListener

  • addListener(eventName: string | symbol, listener: (...args: any[]) => void): CallbackSourceNode<Out>
  • Alias for emitter.on(eventName, listener).

    since

    v0.1.26

    Parameters

    • eventName: string | symbol
    • listener: (...args: any[]) => void
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns CallbackSourceNode<Out>

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) ]
    
    since

    v6.0.0

    Returns (string | symbol)[]

getMaxListeners

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

    since

    v1.0.0

    Returns number

getOptions

listenerCount

  • listenerCount(eventName: string | symbol): number
  • Returns the number of listeners listening to the event named eventName.

    since

    v3.2.0

    Parameters

    • eventName: string | symbol

      The name of the event being listened for

    Returns number

listeners

  • listeners(eventName: string | symbol): Function[]
  • Returns a copy of the array of listeners for the event named eventName.

    server.on('connection', (stream) => {
      console.log('someone connected!');
    });
    console.log(util.inspect(server.listeners('connection')));
    // Prints: [ [Function] ]
    
    since

    v0.1.26

    Parameters

    • eventName: string | symbol

    Returns Function[]

Protected mergeFrame

Protected mergeObject

off

  • off(eventName: string | symbol, listener: (...args: any[]) => void): CallbackSourceNode<Out>
  • Alias for emitter.removeListener().

    since

    v10.0.0

    Parameters

    • eventName: string | symbol
    • listener: (...args: any[]) => void
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns CallbackSourceNode<Out>

onPull

prependListener

  • prependListener(eventName: string | symbol, listener: (...args: any[]) => void): CallbackSourceNode<Out>
  • 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.

    since

    v6.0.0

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: (...args: any[]) => void

      The callback function

        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns CallbackSourceNode<Out>

prependOnceListener

  • prependOnceListener(eventName: string | symbol, listener: (...args: any[]) => void): CallbackSourceNode<Out>
  • 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.

    since

    v6.0.0

    Parameters

    • eventName: string | symbol

      The name of the event.

    • listener: (...args: any[]) => void

      The callback function

        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns CallbackSourceNode<Out>

rawListeners

  • rawListeners(eventName: string | symbol): Function[]
  • Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

    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');
    
    since

    v9.4.0

    Parameters

    • eventName: string | symbol

    Returns Function[]

removeAllListeners

  • 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.

    since

    v0.1.26

    Parameters

    • Optional event: string | symbol

    Returns CallbackSourceNode<Out>

removeListener

  • removeListener(eventName: string | symbol, listener: (...args: any[]) => void): CallbackSourceNode<Out>
  • 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.

    since

    v0.1.26

    Parameters

    • eventName: string | symbol
    • listener: (...args: any[]) => void
        • (...args: any[]): void
        • Parameters

          • Rest ...args: any[]

          Returns void

    Returns CallbackSourceNode<Out>

setMaxListeners

  • 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.

    since

    v0.3.5

    Parameters

    • n: number

    Returns CallbackSourceNode<Out>

setOptions

Static getEventListener

  • getEventListener(emitter: DOMEventTarget | EventEmitter, name: string | symbol): Function[]
  • Returns a list listener for a specific emitter event name.

    Parameters

    • emitter: DOMEventTarget | EventEmitter
    • name: string | symbol

    Returns Function[]

Static listenerCount

  • listenerCount(emitter: EventEmitter, eventName: string | symbol): number
  • deprecated

    since v4.0.0

    Parameters

    • emitter: EventEmitter
    • eventName: string | symbol

    Returns number

Static on

  • on(emitter: EventEmitter, eventName: string, options?: StaticEventEmitterOptions): AsyncIterableIterator<any>
  • Parameters

    • emitter: EventEmitter
    • eventName: string
    • Optional options: StaticEventEmitterOptions

    Returns AsyncIterableIterator<any>

Static once

  • once(emitter: NodeEventTarget, eventName: string | symbol, options?: StaticEventEmitterOptions): Promise<any[]>
  • once(emitter: DOMEventTarget, eventName: string, options?: StaticEventEmitterOptions): Promise<any[]>
  • Parameters

    • emitter: NodeEventTarget
    • eventName: string | symbol
    • Optional options: StaticEventEmitterOptions

    Returns Promise<any[]>

  • Parameters

    • emitter: DOMEventTarget
    • eventName: string
    • Optional options: StaticEventEmitterOptions

    Returns Promise<any[]>