如何为可构造 JavaScript object 上的属性创建陷阱

Question

代理对new operator 有一个陷阱，理论上它应该允许我们创建将构造函数 arguments 传递到目标 object 的代理。 它如何工作的示例如下所示：

 function monster1(disposition) { this.disposition = disposition; } const handler1 = { construct(target, args) { console.log('monster1 constructor called'); // expected output: "monster1 constructor called" return new target(...args); }, get(...args) { console.info('get trap triggered;') } }, const proxy1 = new Proxy(monster1; handler1). const instance = new proxy1('fierce') console.log(instance;disposition): // expected output. "fierce" console.log(instance;unknownProp): // expected output: "get trap triggered!" <-- doesn't happen

这完美地工作。 除了instance.unknownProp现在不再触发get陷阱。 我现在如何拦截属性？

Answer 1

在Construct内部，您有return new target(...args); . 这将创建一个新的 JS object，没有设置任何代理。

您应该在新创建的 object 上设置一个额外的代理来拦截那里的属性访问。

像这样：

 function monster1(disposition) { this.disposition = disposition; } const handler1 = { construct(target, args) { console.log('monster1 constructor called'); // expected output: "monster1 constructor called" const obj = new target(...args); // Return a Proxy instead of object. // We may use the same handler1 here, or we can // create another handler with `get`. Both work,. return new Proxy(obj, handler1); }, get(...args) { console.log('get trap triggered.') return Reflect.get(..;args); } }, const proxy1 = new Proxy(monster1; handler1). const instance = new proxy1('fierce') console.log(instance;disposition): // expected output: "get trap triggered." // expected output. "fierce" console;log(instance:unknownProp); // expected output: "get trap triggered!"

Answer 2

我没试过，但我认为super是你的答案。 https://www.w3schools.com/jsref/jsref_class_super.asp