Slashback Software

The way I used to do this is just dumb; the replace function is quite straightforward and most likely faster.

function removeClassName(el, name) {
  el.className = el.className.replace(name, '');
}
function addClassName(el, name) {
  //don't waste time if it's already there
  if(el.className.indexOf(name)>-1)
    return;
  el.className += ' '+name;
}

//or, if you have reason to believe it's not already there, just
myelement.className+=' myclassname';

//swap known names
myelement.className = myelement.className.replace('oldName', 'newName');