adding style class through javascript

The SO page's first option is incorrect if there are no existing classes on an element. Also, there is a problem with simply deleting and appending to replace a class name in that in some browsers (e.g. MS-IE6) the CSS is order dependent (e.g. h1.classA.classB is not the same as h1.classB.classA).

I use code similar to (E&OE):

function trimAndCondenseSpaces(str)
{
   return str.replace(/^\s+/, '').replace(/\s+$/, '').replace(/\s{2,}/, ' ');
}   // trimAndCondenseSpaces

function getElement(elementOrId)   // Arg is element id or DOM node. Result is DOM node
{
   return (
            typeof elementOrId == 'string' 
            ? document.getElementById(elementOrId) 
            : elementOrId
          );
}   // getElement

function hasClass(elementOrId, className)   // Returns: true if class present, false if absent
{

   // Class name is surrounded by whitespace unless it is the first / last
   var el = getElement(elementOrId); 
   return (new RegExp('(^|\\s)' + className + '(\\s|$)')).test(el.className);
}   // hasClass

function addClass(elementOrId, className)
{
   // Get the element from its id or use the supplied DOM node
   var el = getElement(elementOrId); 
   if (! hasClass(el, className))
      el.className = 
         el.className == ''
         ? el.className + ' ' + className
         : className;
}   // addClass

function dropClass(elementOrId, className)
{
   var el = getElement(elementOrId); 
   if (hasClass(el, className))
      el.className = 
         trimAndCondenseSpaces(
            el.className
               .replace(new RegExp('(^|\\s)' + className + '(\\s|$)'), ' ')
            ); 
}   // dropClass

function replaceClass(elementById, oldClassName, newClassName)   / Adds if old class not found
{
   var el = getElement(elementById);
   el.className = 
      hasClass(el, oldClassName)
      ? trimAndCondenseSpaces(
         el.className
             .replace(new RegExp('(^|\\s)' + oldClassName + '(\\s|$)'), ' ' + newClassName + ' ')
         )
      : addClass(newClassName); 
}   // replaceClass