javascript show select combobox code example

Example 1: javascript get selected option

var e = document.getElementById("selectElementID");
var value=e.selectElement.options[e.selectedIndex].value;// get selected option value
var text=e.options[e.selectedIndex].text;//get the selected option text

Example 2: open select dropdown

$('#MyButton').on("click",function(){
    $("#selecttest").attr("size", 8);
    $("#selecttest").css("position","fixed");
    $('#MyButton').css("margin-left", $("#selecttest").width() + 5);});
$('#selecttest').on("change",function(){
    $("#selecttest").attr("size", 1);});