fetchCache | Caching for the Fetch API in the browser | REST library

  function fetchPlus() {
    ...

    let promise;
    if (fetchCacheGet === null) { // The data is not cached
      promise = fetch(...arguments)
        .then(data => {
          return data.json()
            .then(content => {
              // read the response and cache
              fetchCache.setCache(content);
              const init = {
                'status': 200,
                'statusText': 'SuperSmashingGreat!'
              };
              return new Response(JSON.stringify(content), init); <-- recreate the response and it.
            });
        }); // Store the result in the cache
    } else {
      let dataHeaders = {
        'status': 200,
        'statusText': 'SuperSmashingGreat!'
      };
      promise = new Response(JSON.stringify(fetchCacheGet), dataHeaders); // Programatically create a Response
    }

    return promise;
  }