How to detect input event changes in the textarea of editor ?

[msnitish]

I am planning to check if the entered input is empty or not on every change of event (including backspace).
As soon as the textarea is empty, I want to display a red border around the textarea box.

How do we detect changes like input, keydown, keyup, keypress and simple pastes and cuts in the editor ?

Do we have to write a custom function which detects changes made in the text area ?