EventTarget

eventtarget.js

/**
 * @desc EventTarget
 * @see  《JavaScript高级程序设计（第3版）》 p616
 */
 
function EventTarget(){
  this.handlers = {};    
}

EventTarget.prototype = {
  constructor: EventTarget,

  addHandler: function(type, handler){
    if (typeof this.handlers[type] == "undefined"){
      this.handlers[type] = [];
    }

    this.handlers[type].push(handler);
  },

  fire: function(event){
    if (!event.target){
      event.target = this;
    }
    if (this.handlers[event.type] instanceof Array){
      var handlers = this.handlers[event.type];
      for (var i=0, len=handlers.length; i < len; i++){
        handlers[i](event);
      }
    }            
  },

  removeHandler: function(type, handler){
    if (this.handlers[type] instanceof Array){
      var handlers = this.handlers[type];
      for (var i=0, len=handlers.length; i < len; i++){
        if (handlers[i] === handler){
          break;
        }
      }

      handlers.splice(i, 1);
    }            
  }
};