Extjs multiple inheritance?

Question

I have a question regarding multiple inheritance in ExtJS. While I know I can simply duplicate the code to make it happens, but I want to know if there is any way to code it more efficiently.

I have a customized GridPanel component in my framework, called Kore.ux.grid.GridPanel. It extends Ext.GridPanel with extra common functionalities and provides interface for REST actions.

Soon later, my colleague wanted to have EditorGridPanel to be also implemented in the same manner, ie, she wants it to be editable, and at the same time, have the ability to do REST actions easily.

My question is, is there any way I can extend Ext.EditorGridPanel to take up the customized Kore.ux.grid.GridPanel functionalities?

Sorry for any grammar errors and I can rephrase it if it's confusing. Thanks!!

EDIT

I googled again, and I found threads saying it's impossible. Is there any better coding pattern I should follow if I have this problem?

Thanks!

EDIT AGAIN

So sorry I found the structure that suits me.. Here is the method I found useful to me:

var Common = function(){}   //abstract class
Ext.apply(Common.prototype, {

    a : function(){},
    b: function(){}...

});

Ext.ux.SomePanelA = Ext.extend ( Ext.Panel, {

    stuff : ............

});

Ext.ux.SomePanelB = Ext.extend ( Ext.Panel, {

    diffStuff : ............

});

Ext.applyIf(Ext.ux.SomePanelA.prototype, Common.prototype);
Ext.apply(Ext.ux.SomePanelB.prototype, Common.prototype);

Code Source: http://www.sencha.com/forum/showthread.php?48000-multiple-inheritance&p=228271&viewfull=1#post228271

Please again provide useful suggestions if you think you have a better solution :) Thanks!