externalLogger

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

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

Hierarchy

• EventEmitter
  • Logger
    • LoggerJson
    • LoggerText

Index

Constructors

• constructor

Methods

• _log
• _outputWithConsole
• [captureRejectionSymbol]
• addListener
• emit
• eventNames
• getMaxListeners
• getOptions
• listenerCount
• listeners
• log
• off
• on
• once
• prependListener
• prependOnceListener
• rawListeners
• removeAllListeners
• removeListener
• setMaxListeners
• setOptions

Constructors

externalconstructor

• new Logger(options): Logger

• Overrides EventEmitter.constructor

  Parameters

  • externaloptions: Record<string, any>

  Returns Logger

Methods

external_log

• _log(level, message, data, exception, opts): void

• Parameters

  • externallevel: LogLevel

  • externalmessage: string

  • externaloptionaldata: any

  • externaloptionalexception: unknown

  • externaloptionalopts: Record<string, any>

  Returns void

external_outputWithConsole

• _outputWithConsole(level, line): void

• Parameters

  • externallevel: LogLevel

  • externalline: string

  Returns void

externaloptionalinherited[captureRejectionSymbol]

• [captureRejectionSymbol](error, event, ...args): void

• Inherited from EventEmitter.[captureRejectionSymbol]

  The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

  import { EventEmitter, captureRejectionSymbol } from 'node:events';
  
  class MyClass extends EventEmitter {
    constructor() {
      super({ captureRejections: true });
    }
  
    [captureRejectionSymbol](err, event, ...args) {
      console.log('rejection happened for', event, 'with', err, ...args);
      this.destroy(err);
    }
  
    destroy(err) {
      // Tear the resource down here.
    }
  }

  ---

  Parameters

  • externalerror: Error

  • externalevent: string | symbol

  • externalrest...args: any[]

  Returns void

externalinheritedaddListener

• addListener<E>(eventName, listener): this

• Inherited from EventEmitter.addListener

  Alias for emitter.on(eventName, listener).

  ---

  Parameters

  • externaleventName: string | symbol

  • externallistener: (...args) => void

  Returns this

externalinheritedemit

• emit<E>(eventName, ...args): boolean

• Inherited from EventEmitter.emit

  Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

  Returns true if the event had listeners, false otherwise.

  import { EventEmitter } from 'node: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

  • externaleventName: string | symbol

  • externalrest...args: any[]

  Returns boolean

externalinheritedeventNames

• eventNames(): (string | symbol)[]

• Inherited from EventEmitter.eventNames

  Returns an array listing the events for which the emitter has registered listeners.

  import { EventEmitter } from 'node: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)[]

externalinheritedgetMaxListeners

• getMaxListeners(): number

• Inherited from EventEmitter.getMaxListeners

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

  ---

  Returns number

externalgetOptions

• getOptions(): Record<string, any>

• Returns Record<string, any>

externalinheritedlistenerCount

• listenerCount<E>(eventName, listener): number

• Inherited from EventEmitter.listenerCount

  Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

  ---

  Parameters

  • externaleventName: string | symbol

    The name of the event being listened for

  • externaloptionallistener: (...args) => void

    The event handler function

  Returns number

externalinheritedlisteners

• listeners<E>(eventName): (...args) => void[]

• Inherited from EventEmitter.listeners

  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

  • externaleventName: string | symbol

  Returns (...args) => void[]

externallog

• log(level, message, ...args): void

• Parameters

  • externallevel: LogLevel

  • externalmessage: string

  • externalrest...args: any[]

  Returns void

externalinheritedoff

• off<E>(eventName, listener): this

• Inherited from EventEmitter.off

  Alias for emitter.removeListener().

  ---

  Parameters

  • externaleventName: string | symbol

  • externallistener: (...args) => void

  Returns this

externalinheritedon

• on<E>(eventName, listener): this

• Inherited from EventEmitter.on

  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. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

  import { EventEmitter } from 'node:events';
  const myEE = new EventEmitter();
  myEE.on('foo', () => console.log('a'));
  myEE.prependListener('foo', () => console.log('b'));
  myEE.emit('foo');
  // Prints:
  //   b
  //   a

  ---

  Parameters

  • externaleventName: string | symbol

    The name of the event.

  • externallistener: (...args) => void

    The callback function

  Returns this

externalinheritedonce

• once<E>(eventName, listener): this

• Inherited from EventEmitter.once

  Adds a one-time listener 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. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

  import { EventEmitter } from 'node:events';
  const myEE = new EventEmitter();
  myEE.once('foo', () => console.log('a'));
  myEE.prependOnceListener('foo', () => console.log('b'));
  myEE.emit('foo');
  // Prints:
  //   b
  //   a

  ---

  Parameters

  • externaleventName: string | symbol

    The name of the event.

  • externallistener: (...args) => void

    The callback function

  Returns this

externalinheritedprependListener

• prependListener<E>(eventName, listener): this

• Inherited from EventEmitter.prependListener

  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

  • externaleventName: string | symbol

    The name of the event.

  • externallistener: (...args) => void

    The callback function

  Returns this

externalinheritedprependOnceListener

• prependOnceListener<E>(eventName, listener): this

• Inherited from EventEmitter.prependOnceListener

  Adds a one-time listener 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

  • externaleventName: string | symbol

    The name of the event.

  • externallistener: (...args) => void

    The callback function

  Returns this

externalinheritedrawListeners

• rawListeners<E>(eventName): (...args) => void[]

• Inherited from EventEmitter.rawListeners

  Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

  import { EventEmitter } from 'node:events';
  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

  • externaleventName: string | symbol

  Returns (...args) => void[]

externalinheritedremoveAllListeners

• removeAllListeners<E>(eventName): this

• Inherited from EventEmitter.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.

  ---

  Parameters

  • externaloptionaleventName: string | symbol

  Returns this

externalinheritedremoveListener

• removeListener<E>(eventName, listener): this

• Inherited from EventEmitter.removeListener

  Removes the specified listener from the listener array for the event named eventName.

  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 any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

  import { EventEmitter } from 'node:events';
  class MyEmitter extends EventEmitter {}
  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 indexes 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:

  import { EventEmitter } from 'node:events';
  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

  • externaleventName: string | symbol

  • externallistener: (...args) => void

  Returns this

externalinheritedsetMaxListeners

• setMaxListeners(n): this

• Inherited from EventEmitter.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 to Infinity (or 0) to indicate an unlimited number of listeners.

  Returns a reference to the EventEmitter, so that calls can be chained.

  ---

  Parameters

  • externaln: number

  Returns this

externalsetOptions

• setOptions(options): void

• Parameters

  • externaloptions: Record<string, any>

  Returns void