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backup-indexedb.js

void (async () => {
  const dbName = prompt("What's the name of the database to export?");
  if (!dbName) return;
  try {
    const dbExists = await new Promise(resolve => {
      const request = window.indexedDB.open(dbName);
      request.onupgradeneeded = e => {
        e.target.transaction.abort();
        resolve(false);
      };
      request.onerror = () => resolve(true);
      request.onsuccess = () => resolve(true);
    });

    if (!dbExists) {
      throw new Error('Database does not exist');
    }

    const idbDatabase = await new Promise((resolve, reject) => {
      const request = window.indexedDB.open(dbName);
      request.onerror = () => reject('Could not open the database');
      request.onsuccess = () => resolve(request.result);
    });

    const json = await new Promise((resolve, reject) => {
      const exportObject = {};
      if (idbDatabase.objectStoreNames.length === 0) {
        resolve(JSON.stringify(exportObject));
      } else {
        const transaction = idbDatabase.transaction(
          idbDatabase.objectStoreNames,
          'readonly'
        );
    
        transaction.addEventListener('error', reject);
    
        for (const storeName of idbDatabase.objectStoreNames) {
          const allObjects = [];
          transaction
            .objectStore(storeName)
            .openCursor()
            .addEventListener('success', event => {
              const cursor = event.target.result;
              if (cursor) {
                // Cursor holds value, put it into store data
                allObjects.push(cursor.value);
                cursor.continue();
              } else {
                // No more values, store is done
                exportObject[storeName] = allObjects;
    
                // Last store was handled
                if (
                  idbDatabase.objectStoreNames.length ===
                  Object.keys(exportObject).length
                ) {
                  resolve(JSON.stringify(exportObject));
                }
              }
            });
        }
      }
    });

    // File download function
    const downloadFile = (content, fileName, contentType) => {
      const blob = new Blob([content], { type: contentType });
      const url = URL.createObjectURL(blob);
      const downloadLink = document.createElement('a');
      downloadLink.href = url;
      downloadLink.download = fileName;
      document.body.appendChild(downloadLink);
      downloadLink.click();
      document.body.removeChild(downloadLink);
      URL.revokeObjectURL(url);
    };

    // add datetime in file name
    const now = new Date();
    const timestamp = `${now.getFullYear()}${(now.getMonth() + 1).toString().padStart(2, '0')}${now.getDate().toString().padStart(2, '0')}_${now.getHours().toString().padStart(2, '0')}${now.getMinutes().toString().padStart(2, '0')}`;
    const fileName = `${dbName}_backup_${timestamp}.json`;

    // proceed JSON download
    downloadFile(json, fileName, 'application/json');

    console.log(`Database "${dbName}" has been exported and downloaded as ${fileName}`);
  } catch(error) {
    console.error(error);
  }
})();