Is there a sass tool for Javascript?
<p>Is there a tool like Sass for Javascript? 
To be more specific:</p>

<p>A tool that allows the user to include multiple javascript files via a special syntax and watch for any changes on the files included. Once a change occurs on one or more of those files, the tool should concatenate and compress the files and ideally do some error checking along the way. The results should be included in a single file. </p>

<p>I'm looking for a tool that runs in the background while I'm coding, <strong>not</strong> a server or client side tool like <a href="http://code.google.com/p/minify/" rel="nofollow">minify</a> or less.js</p>
