code: function addClass(elm, name) {
          if (!name) return this
          var cls = className(elm),
              names;
          if (langx.isString(name)) {
              names = name.split(/\s+/g);
          } else {
              names = name;
          }
          names.forEach(function(klass) {
              var re = classRE(klass);
              if (!cls.match(re)) {
                  cls += (cls ? " " : "") + klass;
              }
          });
  
          className(elm, cls);
  
          return this;
      }
docs: /*
  Adds the specified class(es) to each element in the set of matched elements.
  @param {HTMLElement} elm
  @param {String} name