Check If Proxy Object Is Revoked

ECMAScript 6 introduces proxy object, which may be created as revocable. How can I detect if a proxy has been revoked?

Solution 1:

The Proxy constructor only accepts targets and handlers when they are objects and are not revoked proxies. From ProxyCreate,

1. If Type(target) is not Object, throw a TypeError exception.
2. If target is a Proxy exotic object and the value of the [[ProxyHandler]] internal slot of target is null, throw a TypeError exception.

This allows you to check if a value is a revoked proxy: you only need to ensure that it's an object but makes Proxy throw.

Something like this should work:

functionisRevokedProxy(value) {
  try {
    newProxy(value, value);
    returnfalse;
  } catch(err) {
    returnObject(value) === value;
  }
}