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 purposes, it prints out the added listeners.

EventBus.getEvents()

watch

For debugging purposes, add callbacks to fire when events are dispatched.

var onDispatch = function(type) { console.log("[EventBus] Dispatching: " + type) }
var onCallback = function(type) { console.log("[EventBus] Handling: " + type) }
var onAdd = function(type) { console.log("[EventBus] Adding Listener: " + type) }
var onRemove = function(type) { console.log("[EventBus] Removing Listener: " + type) }
EventBus.watch(onDispatch, onCallback, onAdd, onRemove)

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);