onchange dom js 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 value change

function updateInput(ish){
    document.getElementById("fieldname").value = ish;
}