兼容IE8 addEventListener、removeEventListener 函数

//兼容bind函数if(!Function.prototype.bind){    Function.prototype.bind = function(){        if(typeof this !== 'function'){　　　　　　throw new TypeError('Function.prototype.bind - what is trying to be bound is not callable');　　　　}        var _this = this;        var obj = arguments[0];        var ags = Array.prototype.slice.call(arguments,1);        return function(){            _this.apply(obj,ags);        };    };}//兼容addEventListener函数function addEventListener(ele,event,fn){    if(ele.addEventListener){        ele.addEventListener(event,fn,false);    }else{        ele.attachEvent('on'+event,fn.bind(ele));    }}//兼容removeEventListener函数function removeEventListener(ele,event,fn){    if(ele.removeEventListener){        ele.removeEventListener(event,fn,false);    }else{        ele.detachEvent('on'+event,fn.bind(ele));    }}