Simple JavaScript class for managing events in JavaScript

Installation

In a browser

Download eventbus.min.js and add it to your page.

In Node

npm i eventbusjs -S

And then in your code:

var EventBus = require('eventbusjs');

API

addEventListener

// @type - string
// @callback - function
// @scope - the scope where the @callback is defined
EventBus.addEventListener(type, callback, scope)

removeEventListener

// @type - string
// @callback - function
// @scope - the scope where the @callback is defined
EventBus.removeEventListener(type, callback, scope)

hasEventListener

// @type - string
// @callback - function
// @scope - the scope where the @callback is defined
EventBus.hasEventListener(type, callback, scope)

dispatch

// @type - string
// @target - the caller
// @args - pass as many arguments as you want
EventBus.dispatch(type, target, args ...)

getEvents

For debugging purpose, it prints out the added listeners.

EventBus.getEvents()

Usage

function myFunction(event) {
  console.log("myFunction type=" + event.type);
}
EventBus.addEventListener("my_function_event", myFunction);
EventBus.dispatch("my_function_event");

Keeping the scope

var TestClass1 = function() {
  this.className = "TestClass1";
  this.callback = function(event) {
    console.log(this.className + " = type:" + event.type + " / dispatcher:" + event.target.className);
  }
};
var TestClass2 = function() {
  this.className = "TestClass2";
  this.dispatchOurEvent = function() {
    EventBus.dispatch("callback_event", this);
  }
};
var t1 = new TestClass1();
var t2 = new TestClass2();
EventBus.addEventListener("callback_event", t1.callback, t1);
t2.dispatchOurEvent();

Passing additional parameters

var TestClass1 = function() {
  this.className = "TestClass1";
  this.doSomething = function(event, param1, param2) {
    console.log(this.className + ".doSomething");
    console.log("type=" + event.type);
    console.log("params=" + param1 + param2);
    console.log("coming from=" + event.target.className);
  }
};
var TestClass2 = function() {
  this.className = "TestClass2";
  this.ready = function() {
    EventBus.dispatch("custom_event", this, "javascript events", " are really useful");
  }
};

var t1 = new TestClass1();
var t2 = new TestClass2();

EventBus.addEventListener("custom_event", t1.doSomething, t1);
t2.ready();

Example of usage EventBus.removeEventListener

To remove EventListener you have to pass same instance of callback

/* Wrong - callback functions are different instances */
EventBus.addEventListener('EXAMPLE_EVENT', function() {
    console.log('example callback');
});
EventBus.removeEventListener('EXAMPLE_EVENT', function() {
    console.log('example callback');
});

/* Correct - callback function is the same instance */
var handler = function() {
    console.log('example callback');
};
EventBus.addEventListener('EXAMPLE_EVENT', handler);
EventBus.removeEventListener('EXAMPLE_EVENT', handler);