title: knockout.js using $index with if binding
body: <p>I'm trying to show some mark up based on the value of <code>$index</code>, I can display the value but I can't seem to use it with an <code>if</code> binding, what's the best approach here?</p>
  
  <pre><code>&lt;!-- ko if: $index===0 --&gt;
    &lt;div&gt;some mark up here&lt;/div&gt;
  &lt;!-- /ko --&gt;
  </code></pre>