Thanks for your answer.

I still wonder why igNumber and igText did not make this fault, but igDateEditor is.

Hi Duong, 

As Tatsushi pointed, this behavior is triggered from the default browser action for cutting selected text once you drag it with your mouse, after it's highlighted. The difference for all the three editors you're mentioning is that igMaskEditor, igDateEditor and igDatePicker all have default input masks. When cutting value from them while in edit mode the editor executed specific logic to handle deletion correctly, because after the deletion the input mask should remain, but not be cleared. the behavior should be same as if you highlight the text and hit backspace, or delete key on the keyboard. 

Thanks,