function jqLiteAddClass(element, cssClasses) {
  if (!cssClasses || !element.setAttribute) return;

  var existingClasses = _getExistingClasses(element),
      splitClasses = cssClasses.split(' '),
      cssClass;

  for (var i=0; i < splitClasses.length; i++) {
    cssClass = splitClasses[i].trim();
    if (existingClasses.indexOf(' ' + cssClass + ' ') === -1) {
      existingClasses += cssClass + ' ';
    }
  }
  
  element.setAttribute('class', existingClasses.trim());
}
Add a class to an element.
@param {Element} element - The DOM element.
@param {string} cssClasses - Space separated list of class names.