scopeinspect-js is a Chrome extension that utilizes the Chrome DevTools Protocol to programmatically inspect internal JavaScript state that would otherwise be inaccessible, such as WeakSet entries, private class properties, and closure variables. It serves as an archaic answer to this forum post.

Installation

https://developer.chrome.com/docs/extensions/get-started/tutorial/hello-world#load-unpacked

Usage

var Secret = (() => {
  let _secret;
  return function Secret(secret) {
    _secret = secret;
  }
})();
let obj = new Secret(1337);
console.log(await scopeInspect(obj));
// {_secret: 1337}