hasClass / addClass / removeClass

class.js

// http://www.avoid.org/?p=78

function hasClass(el, name) {
  return new RegExp('(\\s|^)' + name + '(\\s|$)').test(el.className);
}

function addClass(el, name) {
  if ( !hasClass(el, name) )
    el.className += (el.className ? ' ' : '') + name;
}

function removeClass(el, name) {
  if ( hasClass(el, name) )
    el.className = el.className.replace(new RegExp('(\\s|^)' + name + '(\\s|$)'), ' ').replace(/^\s+|\s+$/g, '');
}