Proxy returning different value from expected

Question

Just as mentioned in the title, I am using a proxy to hook a WebSocket but, the toString function(accessed using a WebSocket proxy) is returning different values even though the proxy is returning what seems to be the correct function...

Here's an example:

console.log(WebSocket.toString());
unsafeWindow.WebSocket = new Proxy(WebSocket, {
    get(target, p, receiver) {
        console.log(target);
        return target[p]; //supposedly correct
    }
});
console.log(unsafeWindow.WebSocket.toString());

As you can see, instead of returning the original toString value, it is returning what seems to be the toString value of the proxy instead, why is this happening?

Answer 1

You're returning the toString by itself, so when you call that, the this is all "messed up" (see this for a complete overview of how this works). You need to bind it back to target so that the this inside still points to WebSocket:

console.log(WebSocket.toString());

WebSocket = new Proxy(WebSocket, {
    get(target, p, receiver) {
        return target[p].bind(target);
    }
});

console.log(WebSocket.toString());

Also, consider using Reflect.get(target, p, receiver) instead of target[p], depending on what you want to do (see this question for details).