IE8- bind() 函数兼容

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);        };    };}