title: Two sets of parentheses after function call
body: <p>I was looking how <a href="http://docs.angularjs.org/api/ng.$filter" rel="noreferrer">filters</a> works in Angularjs and I saw that we need to send 2 sets of parentheses. </p>
  
  <pre><code>$filter('number')(number[, fractionSize])
  </code></pre>
  
  <p>What does it means and how do we handle it with JavaScript? </p>