casella di testo html js sul cambiamento
<!--
You can use any of the following:
onkeydown, onkeyup or onchange
-->
<input type="text" onkeydown="keydownFunction()"
onkeyup="keyupFunction()" onchange="changeFunction()">
onchange su seleziona tag
<select id="comboA" onchange="getComboA(this)">
<option value="">Select combo</option>
<option value="Value1">Text1</option>
<option value="Value2">Text2</option>
<option value="Value3">Text3</option>
</select>