Definition: The onkeyup event is used to define actions to be taken when a key on the keyboard is released. An onkeyup event is triggered immediately the key is depressed and before the key is released. This is not a reserved word so you can declare your own variable or function called onkeyup but if you do then you will not be able to use this event.
Examples:
<input type="text" onkeyup="myFunction(this)">