<script type="text/javascript" src="/js/ext1.js"></script>
<script type="text/javascript" src="/js/ext2.js"></script>
<script type="text/javascript" src="/js/ext3.js"></script>
ExtJS is valid javascript. You can specify
Code:
Ext.onReady(function(){
alert("test");
});
in multiple pages.
Your big issue is making sure everything is instantiated/created before you start a script that attempts to coordinate behaviors. Might want to delay adding listeners until you are in the last script, i.e.
myPanel.on('render',function(){...});