title: What does colon do in a javascript function parameter
body: <p>I saw in a javascript code written by a young guy this function</p>
  <pre><code>function foo(e:MouseEvent){
     ...
  }
  </code></pre>
  <blockquote>
  <p>I want to know what does <strong>e:MouseEvent</strong> do?</p>
  </blockquote>