Basic emitter in JavaScript

signal-examples.js

// EXAMPLE 1

var formSended = new Signal();
formSended.add(function () { console.log('A'); });
formSended.add(function () { console.log('B'); });

// Put this anywhere in your code
formSended.dispatch();
  // console output => 'A'
  // console output => 'B'


// EXAMPLE 2

var signalWithParams = new Signal();
signalWithParams.add((a, b) => console.log(a + b));

// Put this anywhere in your code
signalWithParams.dispatch(2, 3);
  // console output => 5

signal.js

(function (global) {
  var Signal = function () {
    this._listeners = [];
  };

  Signal.prototype.constructor = Signal;

  Signal.prototype.add = function (handler, priority) {
    this._listeners.push({
      handler: handler,
      priority: (priority === undefined ? 0 : priority)
    });
  };

  Signal.prototype.remove = function (handler) {
    for (var i = this._listeners.length; i >= 0; --i) {
      if (this._listeners[i].handler === handler) {
        this._listeners.splice(i, 1);
      }
    }
  };

  Signal.prototype.removeAll = function () {
    this._listeners = [];
  };

  Signal.prototype.dispatch = function () {
    var args = Array.prototype.slice.call(arguments);
    var sortDesc = function (a, b) {
      return b.priority - a.priority;
    };

    this._listeners.sort(sortDesc).forEach(function (item) {
      item.handler.apply(item.handler, args);
    });
  };

  if (typeof define === 'function' && define.amd) { // AMD
    define(function () { return Signal; });
  } else if (typeof module !== 'undefined' && module.exports) { // node
    module.exports = Signal;
  } else { // browser
    // use string because of Google closure compiler ADVANCED_MODE
    global['Signal'] = Signal;
  }
}(this));