Javascript adding zeros to the beginning of a string (max length 4 chars)
<pre><code>var number = 1310;
</code></pre>

<p>should be left alone.</p>

<pre><code>var number = 120;
</code></pre>

<p>should be changed to "0120";</p>

<pre><code>var number = 10;
</code></pre>

<p>should be changed to "0010";</p>

<pre><code>var number = 7;
</code></pre>

<p>should be changed to "0007";</p>
