initial-sync-data.js

function fullSync(page = 1) {
  let open = indexedDB.open("books", 1);

  // Set up the database schema
  open.onsuccess = evt => {
    let db = open.result;
    fullSyncPage(db, 1);
  };
}

function fullSyncPage(db, page) {
  let pageSize = 50;
  doFetch("/book/offlineSync", { page, pageSize })
    .then(resp => resp.json())
    .then(resp => {
      if (!resp.books) return;
      let books = resp.books;
      let i = 0;
      putNext();

      function putNext() {
        if (i < pageSize) {
          let book = books[i++];
          if (!book) {
            loadDone(db);
            return;
          }

          let transaction = db.transaction("books", "readwrite");
          let booksStore = transaction.objectStore("books");
          booksStore.add(Object.assign(book, { imgSync: 0 })).onsuccess = putNext;
        } else {
          if (books.length > pageSize) {
            fullSyncPage(db, page + 1);
          } else {
            loadDone(db);
          }
        }
      }
    });
}

function loadDone(db) {
  let transaction = db.transaction("syncInfo", "readwrite");
  let syncInfoStore = transaction.objectStore("syncInfo");
  let req = syncInfoStore.get(1);
  req.onsuccess = ({ target: { result } }) => {
    Object.assign(result, { lastLoad: +new Date(), lastLoadStarted: null });
    syncInfoStore.put(result);
  };
}