Currently there is no configuration that supports making "No" button as default for a Confirm dialog in ExtJS. So how to make no button as default?
One way to do this is to get Dialog and mark second button as default.
Here is the code snippet that makes no as default button:
var dialog = Ext.MessageBox.confirm('Confirm', 'Do you really mean it?' ,feedbackFunction).getDialog();
dialog.defaultButton = 2;