title: Chrome Console Object Properties Shown with Angle and Square Brackets
body: <p>When listing properties of an object in the Chrome console, I stumbled upon notations I had never seen before. Indeed, some properties were outlined with <code>&lt;angle-brackets-properties&gt;</code> and the <code>[[double-square-brackets-properties]]</code> notations. Could anyone shed some light on:</p>
  
  <ul>
  <li>What these notations are for</li>
  <li>What are the implications in terms of behaviour/modifiers of these
  properties (enumerable, writable, configurable, etc)</li>
  <li>Whether this can be reproduced by pure Javascript operations, or if this is can only be achieved through native C++ objects</li>
  <li>When this was introduced (ECMAScript spec)</li>
  </ul>
  
  <p>You will find an example below:
  <a href="https://i.stack.imgur.com/R8wSp.png" rel="noreferrer"><img src="https://i.stack.imgur.com/R8wSp.png" alt="enter image description here"></a></p>