whole_func_string: function _addClass(element, className, classRegExp) {
      if (element.className) {
        _removeClass(element, classRegExp);
        element.className += " " + className;
      } else {
        element.className = className;
      }
    }
func_code_string: function _addClass(element, className, classRegExp) {
      if (element.className) {
        _removeClass(element, classRegExp);
        element.className += " " + className;
      } else {
        element.className = className;
      }
    }
func_documentation_string: Remove similiar classes (based on classRegExp)
  and add the desired class name