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);});