undefined variable in jquery code
<p>I asked a question about the undefined value in javascript a few days ago. (<a href="http://stackoverflow.com/questions/7108109/what-is-the-best-way-to-compare-a-value-against-undefined">What is the best way to compare a value against &#39;undefined&#39;?</a>)
I conclude that it is a bad practice to do <code>!== undefined</code> as <code>undefined</code> can be set to 'another' value.</p>

<pre><code>undefined='foo';
var b;
(b !== undefined) // true
</code></pre>

<p>I gave a quick look at the jquery code, I realized that in every part, the author use <code>!== undefined</code> and not <code>typeof var !== "undefined"</code></p>

<pre><code>// Setting one attribute
if ( value !== undefined ) {
// Optionally, function values get executed if exec is true
    exec = !pass &amp;&amp; exec &amp;&amp; jQuery.isFunction(value);
</code></pre>

<p>Is it a possible mistake? Even if I know that we should be crazy to reassign the value of undefined - for the most popular library I think it can cause some mistakes...</p>

<p>Who is in the right way? </p>
