code: function toggleClass( classList, className, on ) {
  		var re = RegExp("(^|\\s)" + className + "(\\s|$)");
  		var classExists = re.test(classList);
  		if (on) {
  			return classExists ? classList : classList + SPACE_STRING + className;
  		} else {
  			return classExists ? trim(classList.replace(re, PLACEHOLDER_STRING)) : classList;
  		}
  	}
docs: --[ toggleClass() ]-------------------------------------------------- adds / removes a className from a string of classNames. Used to manage multiple class changes without forcing a DOM redraw