get value and text from onchange select code example
Example 1: onchange on select 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>
Example 2: javascript input onchange get value
var element = document.getElementById("myInput");
element.onchange = function() {
console.log(element.value);
}