why would you assign this to another variable?
<p>At the start of <a href="http://documentcloud.github.com/underscore/docs/underscore.html" rel="nofollow">the source code for underscore.js</a>, you see this:</p>

<pre><code>var root = this;

var previousUnderscore = root._;
</code></pre>

<p>So the question becomes why didnt the author just write:</p>

<pre><code>var previousUnderscore = this._;
</code></pre>
