手写Bind

Function.prototype.bind2 = function(context){
var self = this;
var args = [].slice.call(arguments,1);
var returnfn = function(){
var args2 = [].slice.call(arguments);
return self.apply(this instanceof returnfn ?this:context,args.concat(args2));
}
function returnFather(){}
returnFather.prototype = this.prototype;
returnfn.prototype = new returnFather();

return returnfn;
}