javascript when select changes code example

Example 1: .on change get value

$('select').on('change', function() {
  alert( this.value );
});

Example 2: js html textbox on change

<!-- 
	You can use any of the following:
	onkeydown, onkeyup or onchange
 -->

<input type="text" onkeydown="keydownFunction()" 
onkeyup="keyupFunction()" onchange="changeFunction()">