JavaScript seeting selectedIndex to be blank for select do not work -

I'm trying to make a default selection to clear a dropdown selection.

If I select the dropdown with HTML, it works, however, when I generate the same dropdown with Javascript, it does not work.

Please

  & lt; Id = "myDropdown" & gt; & Lt; Options & gt; Option 1 & lt; / Options & gt; & Lt; Options & gt; Option 2 & lt; / Options & gt; & Lt; Options & gt; Option 3 & lt; / Options & gt; & Lt; / Select & gt; & Lt; Div id = "yo" & gt; & Lt; / Div & gt; Document.getElementById ("myDropdown"). SelectedIndex = 1 var for my_select = document.createElement ("I select") (var i = 0; i & lt; 3; i ++) {my_select.options [i] = new option (i, i)} my_select .selectedIndex = -1 document.getElementById ("yo"). AppendChild (my_select)   
 Note that the first dropdown is empty, and the second is not.  
  
 
 
 Apparently you select a  of  selectedIndex   element that has not yet been entered in the DOM  
 If you move  my_select.selectedIndex = 1  after the  attachment  So it works fine.  
  var my_select = Document.createElement ("select"); For (var i = 0; i   
.