persistenceMapper.ts

export const persistenceMapper = async (data: any) => {
  const parsed = JSON.parse(data);

  const mapped: any = {};
  const persistEntities: any[] = [];
  const rootQuery = parsed['ROOT_QUERY'];

  mapped['ROOT_QUERY'] = Object.keys(rootQuery).reduce(
    (obj: any, key: string) => {
      if (key === '__typename') return obj;

      if (/@persist$/.test(key)) {
        obj[key] = rootQuery[key];

        if (Array.isArray(rootQuery[key])) {
          const entities = rootQuery[key].map((item: any) => item.__ref);
          persistEntities.push(...entities);
        } else {
          const entity = rootQuery[key].__ref;
          persistEntities.push(entity);
        }
      }

      return obj;
    },
    {__typename: 'Query'},
  );

  persistEntities.reduce((obj, key) => {
    obj[key] = parsed[key];
    return obj;
  }, mapped);

  return JSON.stringify(mapped);
};