前言：学习笔记！

    function test1() {console.log("-----------------");console.log(1);console.log("++++++++++++++++++");}function test2() {console.log("-----------------");console.log(2);console.log("++++++++++++++++++");}function test3() {console.log("-----------------");console.log(3);console.log("++++++++++++++++++");}test1();test2();test3();

需求：先打印‘---------------’ 然后打印 ‘数字’ 最后打印 ‘+++++++++++++++’

 Function.prototype.before = function (cb) {var __self__ = this; //这里的this是指向test1 函数return function () {//保存 this 是因为 return 的函数指向 不是 testcb.apply(__self__, arguments);__self__.apply(__self__, arguments);};};Function.prototype.after = function (cb) {var __self__ = this; //这里的this是指向执行test1.before()后返回的函数return function () {__self__.apply(__self__, arguments);cb(__self__, arguments);};};function test1() {console.log(1);}test1.before(() => {console.log("-----------------");}).after(() => {console.log("++++++++++++++++++");})();