title: const keyword usage in Javascript
body: <p>I was reading the source for a MeteorJS package (<a href="https://github.com/meteor/react-packages/blob/devel/packages/react-meteor-data/createContainer.jsx" rel="nofollow">this one</a>) when I came across this:</p>
  
  <pre><code>const {
    getMeteorData,
    pure = true,
  } = expandedOptions;
  </code></pre>
  
  <p>I did some research to figure out what this code would do, but couldn't find any other instance of <em>const</em> being used like this, or any documentation to clarify it for me.</p>
  
  <p>Any hints, please?</p>