Function.prototype.before = function(beforeFn) {    var slef = this;    console.log(this);    return function() {        console.log(this);        beforeFn.apply(this, arguments);        return slef.apply(this, arguments)    }};Function.prototype.after = function(afterFn) {    var self = this;    return function() {        var res = self.apply(this, arguments);        afterFn.apply(this, arguments);        return res;    }};