事宜绑定机制简朴完成

道理：

• 保护一个事宜数组

• 经由过程apply挪用

var slice = [].slice;
/*
* event control class
* @param {context}
*/
function Event(ctx){
this._ctx = ctx || this;
this._events = {};
}
var EventProto = Event.prototype;
/*
* bind a event
* @param {event} eventType
* @param {fn} function
*/
EventProto.on = function(event, fn){
this._events[event] = this._events[event] || [];
this._events[event].push(fn);
return this;
}
/*
* bind an event but only called one time
* @param {event} eventType
* @param {fn} function
*/
EventProto.Once= function(event, fn){
var self = this;
//when fn is called, remove all event listener
function fnWrap(){
self.off(event, fnWrap);
fn.apply(this, arguments);
}
//to specifiy remove method
fnWrap.fn = fn;
this.on(event, fnWrap);
return this;
}
/*
* unbind an event
* @param {event} eventType
* @param {fn} function
*/
EventProto.off = function(event, fn){
//remove all events
if(!arguments){
this._events = {};
return this;
}
//there are not fn binded
var events = this._events[event];
if(!events) return this;
//remove an type events
if(arguments.length === 1 && typeof event === 'string'){
delete this._events[event];
return this;
}
//remove fn
var handler;
for(var i = 0; i handler = events[i];
if(handler === fn || handler.fn === fn){
events.splice(i, 1);
break;
}
}
return this;
}
/*
* emit
* @param {event}
* @param {fn param}
*/
EventProto.emit = function(event){
var events = this._events[event],
args;
if(events){
events = events.slice(0);
args = slice.call(arguments, 1);
events.forEach(function(event){
event.apply(this._ctx, args);
})
}
return this;
}