NodeJS like EventEmitter. See also NodeJS events documentation

Starting from UB@5.23.9 constructor can accept optional traceAs: string parameter. Is specified, all event handlers calls will be logged using console.traceFunc on Trace level.

  
      const EventEmitter = require('events').EventEmitter
const myObject = {}
// add EventEmitter to myObject
EventEmitter.call(myObject, 'MyObject') // traceAs = 'muObject'
Object.assign(myObject, EventEmitter.prototype)

// In case object created via constructor function
//
// const util = require('util')
// function MyObject() {
//    EventEmitter.call(this, MyObject)
// }
// util.inherits(MyObject, EventEmitter)
//
// var myObject = new MyObject()

// usage
myObject.on('myEvent', function logSumAndNum(num, str){ console.log(num, 'is', str) })
myObject.emit('myEvent', 1, 'two') // output: 1 is two
// Since we specify a `traceAs` parameter, if `Trace` level is enabled in server logging, will add log line:
// YYYYMMDD HHMMSS Trace  MyObject.on(myEvent)->logSumAndNum

// to prevent tracing of some handlers, for example, a handler that already logs its call, `_skipEmitterTrace:true`
// can be added to handler:
function logSumAndNumWOTrace (num, sum) { console.debug('I trace my call by myself'); console.log(num, 'is (wo trace)', str)  }
logSumAndNumWOTrace._skipEmitterTrace = true
myObject.on('myEvent', logSumAndNumWOTrace)

# new EventEmitter (traceAsopt:  string)

Arguments:
  • traceAs: string

    if specified, all event handlers calls will be logged using console.traceFunc on Trace level

Methods

# listenerCount (emitter:  EventEmitter, type:  String) → Number static

Return the number of listeners for a given event.

Arguments:

# addListener (type:  String, listener:  function) → EventEmitter instance

Adds a listener to the end of the listeners array for the specified event. Will emit newListener event on success.

Usage sample:

 Session.on('login', function () {
     console.log('someone connected!');
 });

Returns emitter, so calls can be chained.

Arguments:

# emit (type:  String, eventArgs:  *) → boolean instance

Execute each of the listeners in order with the supplied arguments. Returns true if event had listeners, false otherwise.

Arguments:
  • type: String

    Event name

  • eventArgs: *

    Arguments, passed to listeners

# getMaxListeners () → Number instance

# listeners (type:  String) → Array. instance

Returns an array of listeners for the specified event.

Arguments:

# on (type:  String, listener:  function) → EventEmitter instance

Alias for addListener

Arguments:

# once (type:  String, listener:  function) → EventEmitter instance

Adds a one time listener for the event. This listener is invoked only the next time the event is fired, after which it is removed.

Arguments:

# prependListener (type:  String, listener:  function) → EventEmitter instance

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.

Arguments:

# prependOnceListener (type:  String, listener:  function) → EventEmitter instance

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.

Arguments:

# removeAllListeners (type:  String) → EventEmitter instance

Removes all listeners, or those of the specified event. It's not a good idea to remove listeners that were added elsewhere in the code, especially when it's on an emitter that you didn't create (e.g. sockets or file streams).

Returns emitter, so calls can be chained.

Arguments:

# removeListener (type:  String, listener:  function) instance

Remove a listener from the listener array for the specified event. Caution: changes array indices in the listener array behind the listener. Emits a 'removeListener' event if the listener was removed.

Arguments:

# setMaxListeners (n:  Number) instance

Obviously not all Emitters should be limited to 10. This function allows that to be increased. Set to zero for unlimited.

Arguments: