readme.md

Back up and Restore an IndexedDB Database

This gist provides functions to import and export data from an IndexedDB database as JSON. It's based on Justin Emery's indexeddb-export-import package, but applies some adjustments that reflect better on the current browser landscape (i.e. better developer ergonomics but no support for Internet Explorer).

Usage

For each of the provided functionalities, you need a connected IDBDatabase instance.

Export Data

import { idb } from 'some-database'

import { exportToJson } from 'idb-backup-and-restore.js'

exportToJson(idb)
  .then(result => {
    console.log('Exported JSON string:', result)
  })
  .catch(error => {
    console.error('Something went wrong during export:', error)
  })

Import Data

import { idb } from 'some-database'
import { serializedData } from 'some-serialized-data'

import { importFromJson } from 'idb-backup-and-restore.js'

importFromJson(idb, serializedData)
  .then(() => {
    console.log('Successfully imported data')
  })
  .catch(error => {
    console.error('Something went wrong during import:', error)
  })

Clear Database

Depending on your use case, it can be reasonable to clear a database before importing serialized data:

import { idb } from 'some-database'
import { serializedData } from 'some-serialized-data'

import { importFromJson, clearDatabase } from 'idb-backup-and-restore.js'

clearDatabase(idb)
  .then(() => importFromJson(idb, serializedData))
  .then(() => {
    console.log('Successfully cleared database and imported data')
  })
  .catch(error => {
    console.error('Could not clear & import database:', error)
  })

idb-backup-and-restore.js

/**
 * Export all data from an IndexedDB database
 *
 * @param {IDBDatabase} idbDatabase The database to export from
 * @return {Promise<string>}
 */
export function exportToJson(idbDatabase) {
  return 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))
              }
            }
          })
      }
    }
  })
}

/**
 * Import data from JSON into an IndexedDB database.
 * This does not delete any existing data from the database, so keys may clash.
 *
 * @param {IDBDatabase} idbDatabase Database to import into
 * @param {string}      json        Data to import, one key per object store
 * @return {Promise<void>}
 */
export function importFromJson(idbDatabase, json) {
  return new Promise((resolve, reject) => {
    const transaction = idbDatabase.transaction(
      idbDatabase.objectStoreNames,
      'readwrite'
    )
    transaction.addEventListener('error', reject)

    var importObject = JSON.parse(json)
    for (const storeName of idbDatabase.objectStoreNames) {
      let count = 0
      for (const toAdd of importObject[storeName]) {
        const request = transaction.objectStore(storeName).add(toAdd)
        request.addEventListener('success', () => {
          count++
          if (count === importObject[storeName].length) {
            // Added all objects for this store
            delete importObject[storeName]
            if (Object.keys(importObject).length === 0) {
              // Added all object stores
              resolve()
            }
          }
        })
      }
    }
  })
}

/**
 * Clear a database
 *
 * @param {IDBDatabase} idbDatabase The database to delete all data from
 * @return {Promise<void>}
 */
export function clearDatabase(idbDatabase) {
  return new Promise((resolve, reject) => {
    const transaction = idbDatabase.transaction(
      idbDatabase.objectStoreNames,
      'readwrite'
    )
    transaction.addEventListener('error', reject)

    let count = 0
    for (const storeName of idbDatabase.objectStoreNames) {
      transaction
        .objectStore(storeName)
        .clear()
        .addEventListener('success', () => {
          count++
          if (count === idbDatabase.objectStoreNames.length) {
            // Cleared all object stores
            resolve()
          }
        })
    }
  })
}

Am I correct that the importFromJson function requires that the target db has all the necessary stores created beforehand?

@moniuch Yes, if I remember correctly, this is the case.

@moniuch It simple to modify the code to create stores by JSON before the import.

I may have found a bug - I had a few object stores that were empty. When importing, because there were no records, delete importObject[storeName] was never run. I fixed it by adding a check before the for loop:

      const importObject = JSON.parse(json)
      for (const storeName of idbDatabase.objectStoreNames) {
        // ignore empty stores (we have to do this explicitly or the keys will never be deleted, and the promise will not resolve)
        if(importObject[storeName].length == 0){
            delete importObject[storeName];
            continue;
        }
        let count = 0
        for (const toAdd of importObject[storeName]) {
....