title: @const in javascript?
body: <p>I was reading <a href="http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml" rel="nofollow noreferrer">http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml</a> when I noticed in the Constant section with the annotated comments:</p>
  
  <pre><code>/**
   * The number of seconds in each of the given units.
   * @type {Object.&lt;number&gt;}
   * @const
   */
  </code></pre>
  
  <p>and then the guide goes on with "This allows the compiler to enforce constant-ness."</p>
  
  <p>Is this a v8 thing? where is this documented?</p>
  
  <p><em>My mind is giddy with the possibility that maybe, just maybe, i can provide v8 (or whatever) with type information!</em></p>