UltimateEditor provides client-side event handlers such as OnBeforeClick and OnAfterClick for the button,
and OnBeforeChange and OnAfterChange for the dropdown on the toolbar.

All you have to do is to set the corresponding property of the toolbar item to the client-side method to call
before or after the command to execute if any.

You can also programmatically cancel the event using CancelEvent method so that any default action normally
taken by the implementation as a result of the event will not occur.

Client-Side API is composed of a set of functions for client-side functionality such as event handling and
maintaining editor contents.