dbstorage.js

export function synchronizeFileWithIndexedDb(filename) {
  return new Promise((res, rej) => {
    const db = window.indexedDB.open('SqliteStorage', 1);
    db.onupgradeneeded = () => {
      db.result.createObjectStore('Files', { keypath: 'id' });
    };

    db.onsuccess = () => {
      const req = db.result.transaction('Files', 'readonly').objectStore('Files').get('file');
      req.onsuccess = () => {
        Module.FS_createDataFile('/', filename, req.result, true, true, true);
        res();
      };
    };

    let lastModifiedTime = new Date();
    setInterval(() => {
      const path = `/${filename}`;
      if (FS.analyzePath(path).exists) {
        const mtime = FS.stat(path).mtime;
        if (mtime.valueOf() !== lastModifiedTime.valueOf()) {
          lastModifiedTime = mtime;
          const data = FS.readFile(path);
          db.result.transaction('Files', 'readwrite').objectStore('Files').put(data, 'file');
        }
      }
    }, 1000);
  });
}