//实现一个bind函数 Function.prototype.myBind = function (context) { if (typeof context !== 'function') { throw new TypeError('Error') } var _this = this var argus = [...arguments].slice(1) //返回一个函数 return function F() { //因为返回了一个函数，我们可以new F() 所以需要判断 if (this instanceof F) { return new _this(...arfus, ...arguments, ) } return _this.apply(context, args.concat(...arguments)) } } Function.prototype.call2 = function (context) { debugger // 首先要获取调用call的函数，用this可以获取 context.fn = this; context.fn(); delete context.fn; } //实现一个call函数 Function.prototype.myCall = function (context) { debugger var context = context || window context.fn = this var args = Array.from(arguments).slice(1) var result = context.fn(...args) delete context.fn return result } //实现一个apply函数 Function.prototype.myApply = function (context) { debugger var context = context || window context.fn = this var result if (arguments[1]) { result = context.slice } return result } let handle = { get(target, name) { return name in target ? target[name] : 37 } } let p = new Proxy({}, handler) p.a = 9 p.b = undefined