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);
        }
    }