Index DB with promises

idb.md

IndexedDB Promised

Source

This is a tiny library that mirrors IndexedDB, but replaces the weird IDBRequest objects with promises, plus a couple of other small changes.

Examples

Keyval Store

This is very similar to localStorage, but async. If this is all you need, you may be interested in idb-keyval, you can always upgrade to this library later.

const dbPromise = idb.open('keyval-store', 1, upgradeDB => {
  upgradeDB.createObjectStore('keyval');
});

const idbKeyval = {
  get(key) {
    return dbPromise.then(db => {
      return db.transaction('keyval')
        .objectStore('keyval').get(key);
    });
  },
  set(key, val) {
    return dbPromise.then(db => {
      const tx = db.transaction('keyval', 'readwrite');
      tx.objectStore('keyval').put(val, key);
      return tx.complete;
    });
  },
  delete(key) {
    return dbPromise.then(db => {
      const tx = db.transaction('keyval', 'readwrite');
      tx.objectStore('keyval').delete(key);
      return tx.complete;
    });
  },
  clear() {
    return dbPromise.then(db => {
      const tx = db.transaction('keyval', 'readwrite');
      tx.objectStore('keyval').clear();
      return tx.complete;
    });
  },
  keys() {
    return dbPromise.then(db => {
      const tx = db.transaction('keyval');
      const keys = [];
      const store = tx.objectStore('keyval');

      // This would be store.getAllKeys(), but it isn't supported by Edge or Safari.
      // openKeyCursor isn't supported by Safari, so we fall back
      (store.iterateKeyCursor || store.iterateCursor).call(store, cursor => {
        if (!cursor) return;
        keys.push(cursor.key);
        cursor.continue();
      });

      return tx.complete.then(() => keys);
    });
  }
};

Usage

keyValStore.set('foo', {hello: 'world'});

// logs: {hello: 'world'}
keyValStore.get('foo').then(val => console.log(val));

Set of objects

Imagine we had a set of objects like…

{
  "id": 123456,
  "data": {"foo": "bar"}
}

Upgrading existing DB

const dbPromise = idb.open('keyval-store', 2, upgradeDB => {
  // Note: we don't use 'break' in this switch statement,
  // the fall-through behaviour is what we want.
  switch (upgradeDB.oldVersion) {
    case 0:
      upgradeDB.createObjectStore('keyval');
    case 1:
      upgradeDB.createObjectStore('objs', {keyPath: 'id'});
  }
});

Adding

dbPromise.then(db => {
  const tx = db.transaction('objs', 'readwrite');
  tx.objectStore('objs').put({
    id: 123456,
    data: {foo: "bar"}
  });
  return tx.complete;
});

Getting all

dbPromise.then(db => {
  return db.transaction('objs')
    .objectStore('objs').getAll();
}).then(allObjs => console.log(allObjs));

Getting by ID

dbPromise.then(db => {
  return db.transaction('objs')
    .objectStore('objs').get(123456);
}).then(obj => console.log(obj));

Limitations

Transaction lifetime

At time of writing, all browsers aside from Chrome don't treat promise callbacks as microtasks, or call microtasks incorrectly. This means transactions end by the time promise callbacks are called. In practice, this means you cannot perform transactions that involve waiting for a value, then using it within the same transaction.

const tx = db.transaction('store', 'readwrite');
const store = tx.objectStore('store');
store.get('hello').then(val => store.put(val, 'foo'));

The above will fail in browsers other than Chrome, because the transaction has closed by the time we get to the .put.

You can work around this in Firefox by using a promise polyfill that correctly uses microtasks, such as es6-promise.

Safari

This is a simple wrapper library, so you're exposed to bugs in the underlying implementation. Unfortunately Safari has a lot of these.

API

idb

This is your entry point to the API. It's exposed to the global scope unless you're using a module system such as browserify, in which case it's the exported object.

idb.open(name, version, upgradeCallback)

This method returns a promise that resolves to a DB.

name and version behave as they do in indexedDB.open.

upgradeCallback is called if version is greater than the version last opened. It's similar to IDB's onupgradeneeded. The callback receives an instance of UpgradeDB.

idb.open('keyval-store', 2, upgradeDB => {
  // Note: we don't use 'break' in this switch statement,
  // the fall-through behaviour is what we want.
  switch (upgradeDB.oldVersion) {
    case 0:
      upgradeDB.createObjectStore('keyval');
    case 1:
      upgradeDB.createObjectStore('stuff', {keyPath: ''});
  }
}).then(db => console.log("DB opened!", db));

idb.delete(name)

Behaves like indexedDB.deleteDatabase, but returns a promise.

idb.delete('keyval-store').then(() => console.log('done!'));

DB

Properties:

• Same as equivalent properties on an instance of IDBDatabase:
  • name
  • version
  • objectStoreNames

Methods:

• close - as idbDatabase.close
• transaction - as idbDatabase.transaction, but returns a Transaction

UpgradeDB

As DB, except:

Properties:

• transaction - this is a property rather than a method. It's a Transaction representing the upgrade transaction
• oldVersion - the previous version of the DB seen by the browser, or 0 if it's new

Methods:

• createObjectStore - as idbDatabase.createObjectStore, but returns an ObjectStore
• deleteObjectStore - as idbDatabase.deleteObjectStore

Transaction

Properties:

• complete - a promise. Resolves when transaction completes, rejects if transaction aborts or errors
• Same as equivalent properties on an instance of IDBTransaction:
  • objectStoreNames
  • mode

Methods:

• abort - as idbTransaction.abort
• objectStore - as idbTransaction.objectStore, but returns an ObjectStore

idb.open('keyval-store', 1, upgradeDB => {
  switch (upgradeDB.oldVersion) {
    case 0:
      upgradeDB.createObjectStore('keyval');
  }
}).then(db => {
  const tx = db.transaction('keyval', 'readwrite');
  tx.objectStore('keyval').put('hello', 'world');
  return tx.complete;
}).then(() => console.log("Done!"));

ObjectStore

Properties:

• Same as equivalent properties on an instance of IDBObjectStore:
  • name
  • keyPath
  • indexNames
  • autoIncrement

Methods:

• Same as equivalent methods on an instance of IDBObjectStore, but returns a promise that resolves/rejects based on operation success/failure:
  • put
  • add
  • delete
  • clear
  • get
  • getAll
  • getAllKeys
  • count
• Same as equivalent methods on an instance of IDBObjectStore, but returns a promise that resolves with a Cursor:
  • openCursor
  • openKeyCursor
• deleteIndex - as idbObjectStore.deleteIndex
• Same as equivalent methods on an instance of IDBObjectStore, but returns an Index:
  • createIndex
  • index
• iterateCursor - see below
• iterateKeyCursor - see below

iterateCursor & iterateKeyCursor

Due to the microtask issues in some browsers, iterating over a cursor using promises doesn't always work:

const tx = db.transaction('stuff');
tx.objectStore('stuff').openCursor().then(function cursorIterate(cursor) {
  if (!cursor) return;
  console.log(cursor.value);
  return cursor.continue().then(cursorIterate);
});
tx.complete.then(() => console.log('done'));

So in the mean time, iterateCursor and iterateKeyCursor map to openCursor & openKeyCursor, take identical arguments, plus an additional callback that receives an IDBCursor, so the above example becomes:

const tx = db.transaction('stuff');
tx.objectStore('stuff').iterateCursor(cursor => {
  if (!cursor) return;
  console.log(cursor.value);
  cursor.continue();
});
tx.complete.then(() => console.log('done'));

The intent is to remove iterateCursor and iterateKeyCursor from the library once browsers support promises and microtasks correctly.

Index

Properties:

• Same as equivalent properties on an instance of IDBIndex:
  • name
  • keyPath
  • multiEntry
  • unique

Methods:

• Same as equivalent methods on an instance of IDBIndex, but returns a promise that resolves/rejects based on operation success/failure:
  • get
  • getKey
  • getAll
  • getAllKeys
  • count
• Same as equivalent methods on an instance of IDBIndex, but returns a promise that resolves with a Cursor:
  • openCursor
  • openKeyCursor
• iterateCursor - as objectStore.iterateCursor but over the index
• iterateKeyCursor - as objectStore.iterateKeyCursor but over the index

Cursor

Properties:

• Same as equivalent properties on an instance of IDBCursor:
  • direction
  • key
  • primaryKey
  • value

Methods:

• Same as equivalent methods on an instance of IDBCursor, but returns a promise that resolves/rejects based on operation success/failure:
  • update
  • delete
• Same as equivalent methods on an instance of IDBCursor, but returns a promise that resolves with a Cursor:
  • advance
  • continue
  • continuePrimaryKey