@how to know where onChange event is happening code example

Example 1: 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()">

Example 2: javascript input onchange get value

var element = document.getElementById("myInput");
element.onchange = function() {
  console.log(element.value);
}