code: function empty(a) {
      var hasLength = typeof a === 'string' ||
        Array.isArray(a);
      if (hasLength) {
        return !a.length;
      }
      if (a instanceof Object) {
        return !Object.keys(a).length;
      }
      return false;
    }
docs: Returns true if given value is [], {} or ''
  @method empty