onchange function of JavaScript calling in lambda function

Lambda function is using JavaScript We want a drop down button which list of requests When ever we select a request in from the drop down it should update in the query before running the query After finishing the query execution it should not reset the service name drop down

exports.handler = function myFunction(event,context) { var x = document.getElementById("mySelect").value; selectService=x }

        <tr>
            <td>Select Service</td><td><select id="mySelect"  name="selectService" onchange="myFunction()">
            <option selected="${selectService==="END"?"selected":""}" value="END">END</option>
             <option selected="${selectService==="START"?"selected":""}" value="START">START</option>
            </select></td>
        </tr>