how to add onchange event in javascript 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 add function to onchange event

transport_select.setAttribute("onchange", function(){toggleSelect(transport_select_id);});
// or
transport_select.onchange = function(){toggleSelect(transport_select_id);};