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JS Proxy - real usecases

JavaScript

proxy.js Raw #

// https://javascript.plainenglish.io/the-battle-of-isolation-proxy-vs-web-workers-vs-iframe-in-frontend-development-%EF%B8%8F-3eaeef99a11d

// 1 
const sandbox = new Proxy(window, {
  get(target, key) {
    if (key === 'document') {
      throw new Error('No access to DOM!');
    }
    return Reflect.get(target, key);
  },
  set(target, key, value) {
    if (key === 'location') return false;
    return Reflect.set(target, key, value);
  }
});

// Running plugin code in sandbox
(function(window) {
  try {
    window.document.title = 'Hacked!'; // Triggers exception
  } catch (err) {
    console.error('Illegal operation intercepted:', err);
  }
})(sandbox);



// 2
const audit = new Proxy(console, {
  get(target, key) {
    if (key === 'log') return (...args) => {
      recordLog(args); // Log recording
      target[key](...args);
    };
    return target[key];
  }
});

sandbox.console = audit;