原生js 通用事件绑定

 /*原文地址：http://ejohn.org/blog/flexible-javascript-events/*/
　　　　http://blog.csdn.net/qi1271199790/article/details/53458043
     /**
      * [addEvent &&removeEvent description]
      * @param {[obj]}   obj  [绑定事件的对象]
      * @param {str}   type [绑定的事件的名称]
      * @param {Function} fn   [事件触发的回调函数]
      */
     var txt=document.getElementById('txt');
     function addEvent(obj,type,fn){
         if(obj.attachEvent){
             obj['e'+type+fn] = fn;
             obj[type+fn] = function(){
                 obj['e'+type+fn](window.event);
             };
             obj.attachEvent('on'+type,obj[type+fn]);
         }else{
             obj.addEventListener(type,fn,false);
         }
     }
     function removeEvent(obj,type,fn){
         if(obj.detachEvent()){
             obj.detachEvent('on'+type,obj[type+fn]);
             obj[type+fn] = null;
         }else{
             obj.removeEventListener(type,fn,false);
         }
     }