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.
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:
    //<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.