HTML

drop down onchange javascript

 <select id="ddlFruits">
    <option value=""></option>
    <option value="1">Apple</option>
    <option value="2">Mango</option>
    <option value="3">Orange</option>
</select>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $("#ddlFruits").change(function () {
            var selectedText = $(this).find("option:selected").text();
            var selectedValue = $(this).val();
            alert("Selected Text: " + selectedText + " Value: " + selectedValue);
        });
    });
</script>