如何在Javascript中检查es6代理的类型？

Question

I am working with ES6 Proxy. I have created a proxy of an array, now when i check the type of proxy it is giving me as Object type.

Question:

How can i check if the proxy i have created was for array or object?

Example:

 const arr = ['a', 'b', 'c']; const arrProxy = new Proxy(arr, {}); alert(typeof(arrProxy));

UPDATE (SOLUTION): Instead of using typeof , we should use Array.isArray

const arr = ['a', 'b', 'c'];

const arrProxy = new Proxy(arr, {});

alert(Array.isArray(arrProxy));

Answer 1

You can't tell that a proxy is a proxy. That's part of the point of them, they provide a facade (one you can't detect) around another object.

As far as code looking at your arrProxy can tell, it's an array:

 const arr = ['a', 'b', 'c']; const arrProxy = new Proxy(arr, {}); console.log(Array.isArray(arrProxy)); // true

Separately: typeof is very general, it gives you "object" for a huge range of things: Anything that's of an object (not primitive) type (including null ). So typeof new Map() , typeof new Set() , typeof null , typeof document (on browsers), etc., will all give you "object" . (Also note that typeof is an operator, not a function; no need for the () in your code sample.)

Answer 2

There is also one way to do this using instanceof :

if (arrProxy instanceof Array) {
   console.log('This is an array!');
}

Answer 3

As other answers suggest, you cannot tell if something is a proxy.

So you might need to implement it yourself.

Here is an example from: https://exploringjs.com/deep-js/ch_proxies.html#transparent-virtualization-and-handler-encapsulation

const proxies = new WeakSet();

export function createProxy(obj) {
  const handler = {};
  const proxy = new Proxy(obj, handler);
  proxies.add(proxy);
  return proxy;
}

export function isProxy(obj) {
  return proxies.has(obj);
}