title: Javascript double arrow functions
body: <p>This function is a click handler.</p>
  <p><code>const select = num =&gt; () =&gt; value += num;</code></p>
  <p>It has 2 arrows !!</p>
  <ol>
  <li>Why? Could you use:
  <code>const select = (num) =&gt; value += num;</code></li>
  </ol>
  <p>if not, why not.</p>
  <ol start="2">
  <li>How would
  <code>const select = num =&gt; () =&gt; value += num;</code> ?
  look as a regular function</li>
  </ol>