code: function(attr, index, attrCamel) {
        return this.each(function(i, el) {
          if (attr !== undefined) {
            attrCamel = u.toCamel(u.toDash(attr));
            if ((index = el[u._id]) !== undefined) {
              el.dataset ? delete el.dataset[attrCamel] : el.removeAttribute('data-' + attr);
              delete u._data[index][attrCamel];
            }
          }
        });
      }
docs: removeData method
  remove data attribute
  @param  {string}    attr        - attribute name
  @param  {undefined} [index]     - index placeholder
  @param  {undefined} [attrCamel] - placeholder for attribute name in camelCase
  @return {object}                  this