Quote Originally Posted by usha.basavaraju View Post
Trying to migrate from ext2 to ext4.
Used compatability file also.But still getting this error
Error: [Ext.extend] Attempting to extend from a class which has not been loaded on the page.
javascript//ext-4.1.1a/ext-all-debug.js
Line 4391

Please help..
It seems that you are trying to extend ExtJS class which does not exists in ExtJS4 anymore. You can try to use ext-all-dev.js instead of ext-all-debug.js. ext-all-dev.js logs many useful informations into browser's console.
You can also set breakpoint into ext-all-dev.js to line 5908 (impl. if Ext.extend) and see the name of non-existing superclass.
Code around the line 5908:
Code:
    //<feature classSystem.backwardsCompatible>
    // Backwards compatible
    Ext.extend = function(subclass, superclass, members) {
        if (arguments.length === 2 && Ext.isObject(superclass)) {
            members = superclass;
            superclass = subclass;
            subclass = null;
        }

        var cls;

        if (!superclass) {
            Ext.Error.raise("Attempting to extend from a class which has not been loaded on the page.");
        }
Note that in ExtJS4 you should use Ext.define instead of Ext.extend to define a new class/subcalss.