ExtJS
ExtJS ComboBox doesn't advertise, in its documentation, any way to get the selected index of a ComboBox.
In ExtJS you can create ComboBox which loads data from the server.
After much debugging I realized that in creating dialogs using Ext.LayoutDialog class of ExtJS library we must specify the configuration for east, west, north and south properties, as required, in the LayoutDialog config (see below for more requirements, details and a working example).
This is a sporadic error that I have seen in Firefox browsers while using the Ext JS components.
