title: How to test if an object is a Proxy?
body: <p>I would like to test if a JavaScript object is a <a href="http://www.ecma-international.org/ecma-262/6.0/#sec-proxy-objects">Proxy</a>. The trivial approach</p>
  
  <pre><code>if (obj instanceof Proxy) ...
  </code></pre>
  
  <p>doesn't work here, nor does traversing the prototype chain for <code>Proxy.prototype</code>, since all relevant operations are effectively backed by the underlying target.</p>
  
  <p>Is it possible to test if an arbitrary object is a Proxy?</p>