怎么用JavaScript获取DropDownList选中得值，再添加到listbox中

怎么用JavaScript获取DropDownList选中得值，再添加到listbox中   

 var   select1   =   document.all.<%=   yourDropDownList.ClientID   %>;  

  var   select1value   =   select1.options[select1.selectedIndex].value;  

  var   select1Text   =   select1.options[select1.selectedIndex].innerText;  

  var   select2   =   document.all.<%=   yourListBox.ClientID   %>;  

  var   oOption   =   document.createElement("OPTION");  

  select2.options.add(oOption);  

  oOption.innerText   =   select1Text    

  oOption.Value   =   select1value   ;