It seems a Ext JS bug (version 4.07). After selecting value in a combo and typing several characters validation is not executed. The same trouble for Ext.form.field.ComboBox docs (directly insert in Code Editor).
For example try:
How to sort out this issue? Thanks.Code:Ext.create('Ext.form.ComboBox', { renderTo: Ext.getBody(), store : [ '1pt', '2pt', '3pt' ], editable: true, regex: /^1pt|2pt|3pt|4pt$/, });