Calling javascript functions from drop down

Question

I have this HTML code at the moment:

Theme

    
 Choose theme
        
 
            


        

Answer 1

  Default
  Theme 1
  Theme 2  
  Theme 3


document.getElementById("myList").onchange = function() {
   var sheet=document.getElementById("myList").value;

   if(sheet=="one"){
   setActiveStyleSheet("theme1");
   }
   else if(sheet=="two"){
   setActiveStyleSheet("theme2");
   }
   else if(sheet=="three"){
   setActiveStyleSheet("theme3");
   }
   else{
   setActiveStyleSheet("default");
   }
   return false
};