using jquery in chrome extension
You need to change the order of your script tag to allow jQuery to load first:
<script type="text/javascript" src="jquery-1.9.1.min.js"></script><script type="text/javascript" src="popup.js"></script>
Change the order .You have to load the jquery core plugin first and then then other plugins
<script type="text/javascript" src="jquery-1.9.1.min.js"></script><script type="text/javascript" src="popup.js"></script>