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externalLogger

This is an abstract class that should be extended by custom logger classes.

this._log() method must be implemented by them.

Hierarchy

Index

Constructors

externalconstructor

  • new Logger(options: Record<string, any>): Logger
  • Parameters

    • externaloptions: Record<string, any>

    Returns Logger

Properties

staticexternalreadonlycaptureRejectionSymbol

captureRejectionSymbol: typeof captureRejectionSymbol

staticexternalcaptureRejections

captureRejections: boolean

Sets or gets the default captureRejection value for all emitters.

staticexternaldefaultMaxListeners

defaultMaxListeners: number

staticexternalreadonlyerrorMonitor

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.

Methods

external_log

  • _log(level: LogLevel, message: string, data?: any, exception?: Exception, opts?: Record<string, any>): void
  • Parameters

    • externallevel: LogLevel
    • externalmessage: string
    • externaloptionaldata: any
    • externaloptionalexception: Exception
    • externaloptionalopts: Record<string, any>

    Returns void

external_outputWithConsole

  • _outputWithConsole(level: LogLevel, line: string): void
  • Parameters

    • externallevel: LogLevel
    • externalline: string

    Returns void

externaladdListener

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

    @since

    v0.1.26


    Parameters

    • externaleventName: string | symbol
    • externallistener: (...args: any[]) => void

    Returns Logger

externalemit

  • emit(eventName: string | symbol, ...args: any[]): 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
    @since

    v0.1.26


    Parameters

    • externaleventName: string | symbol
    • externalrest...args: any[]

    Returns boolean

externaleventNames

  • 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)[]

externalgetMaxListeners

  • 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

externalgetOptions

  • getOptions(): Record<string, any>
  • Returns Record<string, any>

externallistenerCount

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

    @since

    v3.2.0


    Parameters

    • externaleventName: string | symbol

      The name of the event being listened for

    Returns number

externallisteners

  • 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

    • externaleventName: string | symbol

    Returns Function[]

externallog

  • log(level: LogLevel, message: string, ...args: any[]): void
  • Parameters

    • externallevel: LogLevel
    • externalmessage: string
    • externalrest...args: any[]

    Returns void

externaloff

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

    @since

    v10.0.0


    Parameters

    • externaleventName: string | symbol
    • externallistener: (...args: any[]) => void

    Returns Logger

externalon

  • on(eventName: string | symbol, listener: (...args: any[]) => void): Logger
  • 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
    @since

    v0.1.101


    Parameters

    • externaleventName: string | symbol

      The name of the event.

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

      The callback function

    Returns Logger

externalonce

  • once(eventName: string | symbol, listener: (...args: any[]) => void): Logger
  • 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
    @since

    v0.3.0


    Parameters

    • externaleventName: string | symbol

      The name of the event.

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

      The callback function

    Returns Logger

externalprependListener

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

    • externaleventName: string | symbol

      The name of the event.

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

      The callback function

    Returns Logger

externalprependOnceListener

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

    • externaleventName: string | symbol

      The name of the event.

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

      The callback function

    Returns Logger

externalrawListeners

  • 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

    • externaleventName: string | symbol

    Returns Function[]

externalremoveAllListeners

  • removeAllListeners(event?: string | symbol): Logger
  • 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

    • externaloptionalevent: string | symbol

    Returns Logger

externalremoveListener

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

    • externaleventName: string | symbol
    • externallistener: (...args: any[]) => void

    Returns Logger

externalsetMaxListeners

  • setMaxListeners(n: number): Logger
  • 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

    • externaln: number

    Returns Logger

externalsetOptions

  • setOptions(options: Record<string, any>): void
  • Parameters

    • externaloptions: Record<string, any>

    Returns void

staticexternalgetEventListeners

  • getEventListeners(emitter: EventEmitter | _DOMEventTarget, name: string | symbol): 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]
    }
    @since

    v15.2.0, v14.17.0


    Parameters

    • externalemitter: EventEmitter | _DOMEventTarget
    • externalname: string | symbol

    Returns Function[]

staticexternallistenerCount

  • listenerCount(emitter: EventEmitter, eventName: string | symbol): 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
    @since

    v0.9.12

    @deprecated

    Since v3.2.0 - Use listenerCount instead.


    Parameters

    • externalemitter: EventEmitter

      The emitter to query

    • externaleventName: string | symbol

      The event name

    Returns number

staticexternalon

  • on(emitter: EventEmitter, eventName: string, options?: StaticEventEmitterOptions): 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());
    @since

    v13.6.0, v12.16.0


    Parameters

    • externalemitter: EventEmitter
    • externaleventName: string

      The name of the event being listened for

    • externaloptionaloptions: StaticEventEmitterOptions

    Returns AsyncIterableIterator<any>

    that iterates eventName events emitted by the emitter

staticexternalonce

  • once(emitter: _NodeEventTarget, eventName: string | symbol, options?: StaticEventEmitterOptions): Promise<any[]>
  • once(emitter: _DOMEventTarget, eventName: string, options?: StaticEventEmitterOptions): 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!
    @since

    v11.13.0, v10.16.0


    Parameters

    • externalemitter: _NodeEventTarget
    • externaleventName: string | symbol
    • externaloptionaloptions: StaticEventEmitterOptions

    Returns Promise<any[]>

staticexternalsetMaxListeners

  • setMaxListeners(n?: number, ...eventTargets: (EventEmitter | _DOMEventTarget)[]): void
  • const {
    setMaxListeners,
    EventEmitter
    } = require('events');

    const target = new EventTarget();
    const emitter = new EventEmitter();

    setMaxListeners(5, target, emitter);
    @since

    v15.4.0


    Parameters

    • externaloptionaln: number

      A non-negative number. The maximum number of listeners per EventTarget event.

    • externalrest...eventTargets: (EventEmitter | _DOMEventTarget)[]

    Returns void