/
EventTarget.js
88 lines (75 loc) · 2.32 KB
/
EventTarget.js
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/**
* A generic base to inherit from for any object
* that needs event handling.
* @class EventTarget
* @constructor
*/
function EventTarget(){
/**
* The array of listeners for various events.
* @type Object
* @property _listeners
* @private
*/
this._listeners = {};
}
EventTarget.prototype = {
//restore constructor
constructor: EventTarget,
/**
* Adds a listener for a given event type.
* @param {String} type The type of event to add a listener for.
* @param {Function} listener The function to call when the event occurs.
* @return {void}
* @method addListener
*/
addListener: function(type, listener){
if (!this._listeners[type]){
this._listeners[type] = [];
}
this._listeners[type].push(listener);
},
/**
* Fires an event based on the passed-in object.
* @param {Object|String} event An object with at least a 'type' attribute
* or a string indicating the event name.
* @return {void}
* @method fire
*/
fire: function(event){
if (typeof event == "string"){
event = { type: event };
}
if (typeof event.target != "undefined"){
event.target = this;
}
if (typeof event.type == "undefined"){
throw new Error("Event object missing 'type' property.");
}
if (this._listeners[event.type]){
//create a copy of the array and use that so listeners can't chane
var listeners = this._listeners[event.type].concat();
for (var i=0, len=listeners.length; i < len; i++){
listeners[i].call(this, event);
}
}
},
/**
* Removes a listener for a given event type.
* @param {String} type The type of event to remove a listener from.
* @param {Function} listener The function to remove from the event.
* @return {void}
* @method removeListener
*/
removeListener: function(type, listener){
if (this._listeners[type]){
var listeners = this._listeners[type];
for (var i=0, len=listeners.length; i < len; i++){
if (listeners[i] === listener){
listeners.splice(i, 1);
break;
}
}
}
}
};