Is it possible to use JS to open an HTML select to show its option list? [duplicate]

Answer 1

  html5
  javascript
  jquery
  css
  sencha

By jQuery:

var myDropDown=$("#myDropDown");
var length = $('#myDropDown> option').length;
//open dropdown
myDropDown.attr('size',length);
//close dropdown
myDropDown.attr('size',0);

By javascript:

var myDropDown=document.getElementById("myDropDown");
var length = myDropDown.options.length;
//open dropdown
myDropDown.size = length;
//close dropdown
myDropDown.size = 0;

Copied from: Open close select