.map() second argument of the callback function
<p>What is the purpose of the second argument in the callback function <code>.map()</code>?</p>

<p>I think it is not necessary because you can use <code>this</code> instead:</p>

<pre><code>&gt; $('p').map(function (index, element) {
      return this===element;
});
[true, true, true, true]
</code></pre>
