fake-indexeddb

What is fake-indexeddb?

The fake-indexeddb npm package is a mock implementation of the IndexedDB API, which is useful for testing and development purposes. It allows developers to simulate IndexedDB operations without relying on a real browser environment.

What are fake-indexeddb's main functionalities?

Creating a Database

This feature allows you to create a new IndexedDB database and an object store within it. The code sample demonstrates how to open a database, handle the upgrade event to create an object store, and log the success event.

const { indexedDB } = require('fake-indexeddb');
const request = indexedDB.open('test-db', 1);
request.onupgradeneeded = function(event) {
  const db = event.target.result;
  db.createObjectStore('store', { keyPath: 'id' });
};
request.onsuccess = function(event) {
  const db = event.target.result;
  console.log('Database created:', db);
};

Adding Data to Object Store

This feature allows you to add data to an object store within the IndexedDB database. The code sample demonstrates how to open a database, create a transaction, add data to the object store, and log the completion of the transaction.

const { indexedDB } = require('fake-indexeddb');
const request = indexedDB.open('test-db', 1);
request.onsuccess = function(event) {
  const db = event.target.result;
  const transaction = db.transaction('store', 'readwrite');
  const store = transaction.objectStore('store');
  store.add({ id: 1, name: 'John Doe' });
  transaction.oncomplete = function() {
    console.log('Data added');
  };
};

Retrieving Data from Object Store

This feature allows you to retrieve data from an object store within the IndexedDB database. The code sample demonstrates how to open a database, create a transaction, retrieve data from the object store, and log the retrieved data.

const { indexedDB } = require('fake-indexeddb');
const request = indexedDB.open('test-db', 1);
request.onsuccess = function(event) {
  const db = event.target.result;
  const transaction = db.transaction('store', 'readonly');
  const store = transaction.objectStore('store');
  const getRequest = store.get(1);
  getRequest.onsuccess = function() {
    console.log('Data retrieved:', getRequest.result);
  };
};

Other packages similar to fake-indexeddb

indexeddbshim

The indexeddbshim package is a polyfill that provides a full implementation of the IndexedDB API for browsers that do not support it natively. Unlike fake-indexeddb, which is primarily for testing, indexeddbshim aims to provide a real IndexedDB experience in environments where it is not available.

localforage

LocalForage is a library that provides a simple API for offline storage, using IndexedDB, WebSQL, or localStorage under the hood. It abstracts away the differences between these storage mechanisms, making it easier to use. While fake-indexeddb is focused on testing, LocalForage is designed for actual application use.

dexie

Dexie is a wrapper library for IndexedDB that provides a more developer-friendly API and additional features like versioning and schema management. It is designed for real-world use in applications, whereas fake-indexeddb is intended for testing purposes.

README

fake-indexeddb

This is a pure JS in-memory implementation of the IndexedDB API. Its main utility is for testing IndexedDB-dependent code in Node.js.

Installation

npm install --save-dev fake-indexeddb

Use

Functionally, it works exactly like IndexedDB except data is not persisted to disk.

The easiest way to use it is to import fake-indexeddb/auto, which will put all the IndexedDB variables in the global scope. (Both import and require are supported, use whichever you like, but the examples here are all import.)

import "fake-indexeddb/auto";

var request = indexedDB.open("test", 3);
request.onupgradeneeded = function () {
    var db = request.result;
    var store = db.createObjectStore("books", {keyPath: "isbn"});
    store.createIndex("by_title", "title", {unique: true});

    store.put({title: "Quarry Memories", author: "Fred", isbn: 123456});
    store.put({title: "Water Buffaloes", author: "Fred", isbn: 234567});
    store.put({title: "Bedrock Nights", author: "Barney", isbn: 345678});
}
request.onsuccess = function (event) {
    var db = event.target.result;

    var tx = db.transaction("books");

    tx.objectStore("books").index("by_title").get("Quarry Memories").addEventListener("success", function (event) {
        console.log("From index:", event.target.result);
    });
    tx.objectStore("books").openCursor(IDBKeyRange.lowerBound(200000)).onsuccess = function (event) {
        var cursor = event.target.result;
        if (cursor) {
            console.log("From cursor:", cursor.value);
            cursor.continue();
        }
    };
    tx.oncomplete = function () {
        console.log("All done!");
    };
};

Alternatively, you can explicitly import individual IndexedDB variables:

import {
    indexedDB,
    IDBCursor,
    IDBCursorWithValue,
    IDBDatabase,
    IDBFactory,
    IDBIndex,
    IDBKeyRange,
    IDBObjectStore,
    IDBOpenDBRequest,
    IDBRequest,
    IDBTransaction,
    IDBVersionChangeEvent,
} from "fake-indexeddb";

// The rest is the same as above.

Like any imported variable, you can rename it if you want, for instance if you don't want to conflict with built-in IndexedDB variables:

import {
    indexedDB as fakeIndexedDB,
} from "fake-indexeddb";

TypeScript

As of version 4, fake-indexeddb includes TypeScript types. As you can see in types.d.ts, it's just using TypeScript's built-in IndexedDB types, rather than generating types from the fake-indexeddb code base. The reason I did this is for compatibility with your application code that may already be using TypeScript's IndexedDB types, so if I used something different for fake-indexeddb, it could lead to spurious type errors. In theory this could lead to other errors if there are differences between Typescript's IndexedDB types and fake-indexeddb's API, but currently I'm not aware of any difference. See issue #23 for more discussion.

Dexie and other IndexedDB API wrappers

If you import fake-indexeddb/auto before importing dexie, it should work:

import "fake-indexeddb/auto";
import Dexie from "dexie";

const db = new Dexie("MyDatabase");

The same likely holds true for other IndexedDB API wrappers like idb.

Alternatively, if you don't want to modify the global scope, then you need to explicitly pass the objects to Dexie:

import Dexie from "dexie";
import { indexedDB, IDBKeyRange } from "fake-indexeddb";

const db = new Dexie("MyDatabase", { indexedDB: indexedDB, IDBKeyRange: IDBKeyRange });

Jest

To use fake-indexeddb in a single Jest test suite, require fake-indexeddb/auto at the beginning of the test file, as described above.

To use it on all Jest tests without having to include it in each file, add the auto setup script to the setupFiles in your Jest config:

{
    "setupFiles": [
        "fake-indexeddb/auto"
    ]
}

jsdom (often used with Jest)

As of version 5, fake-indexeddb no longer includes a structuredClone polyfill. This mostly affects old environments like unsupported versions of Node.js, but it also affects jsdom, which is often used with Jest and other testing frameworks.

There are a few ways you could work around this. You could include your own structuredClone polyfill by installing core-js and importing its polyfill before you use fake-indexeddb:

import "core-js/stable/structured-clone";
import "fake-indexeddb/auto";

Or, you could manually include the Node.js structuredClone implementation in a jsdom environment:

// FixJSDOMEnvironment.ts

import JSDOMEnvironment from 'jest-environment-jsdom';

// https://github.com/facebook/jest/blob/v29.4.3/website/versioned_docs/version-29.4/Configuration.md#testenvironment-string
export default class FixJSDOMEnvironment extends JSDOMEnvironment {
  constructor(...args: ConstructorParameters<typeof JSDOMEnvironment>) {
    super(...args);

    // FIXME https://github.com/jsdom/jsdom/issues/3363
    this.global.structuredClone = structuredClone;
  }
}

// jest.config.js

/** @type {import('jest').Config} */
const config = {
  testEnvironment: './FixJSDOMEnvironment.ts',
};

module.exports = config;

Hopefully a future version of jsdom will no longer require these workarounds.

Wiping/resetting the indexedDB for a fresh state

If you are keeping your tests completely isolated you might want to "reset" the state of the mocked indexedDB. You can do this by creating a new instance of IDBFactory, which lets you have a totally fresh start.

import "fake-indexeddb/auto";
import { IDBFactory } from "fake-indexeddb";

// Whenever you want a fresh indexedDB
indexedDB = new IDBFactory();

With PhantomJS and other really old environments

PhantomJS (and other really old environments) are missing tons of modern JavaScript features. In fact, that may be why you use fake-indexeddb in such an environment! Prior to v3.0.0, fake-indexeddb imported core-js and automatically applied its polyfills. However, since most fake-indexeddb users are not using really old environments, I got rid of that runtime dependency in v3.0.0. To work around that, you can import core-js yourself before you import fake-indexeddb, like:

import "core-js/stable";
import "fake-indexeddb/auto";

Quality

Here's a comparison of fake-indexeddb and real browser IndexedDB implementations on the W3C IndexedDB test suite as of March 18, 2019:

Implementation	Percentage of files that pass completely
Chrome 73	99%
Firefox 65	97%
Safari 12	92%
fake-indexeddb 3.0.0	87%
Edge 18	61%

For browsers, I ran http://w3c-test.org/tools/runner/index.html and counted the passes. For fake-indexeddb, I ran npm run test-w3c.

87% is pretty good, right? Especially considering that fake-indexeddb runs in Node.js where failure is guaranteed for tests involving browser APIs like Web Workers. There are definitley still some weak points of fake-indexeddb, most of which are described in src/test/web-platform-tests/run-all.js. Your app will probably run fine, though.

Potential applications:

1. Use as a mock database in unit tests.

2. Use the same API in Node.js and in the browser.

3. Support IndexedDB in old or crappy browsers.

4. Somehow use it within a caching layer on top of IndexedDB in the browser, since IndexedDB can be kind of slow.

5. Abstract the core database functions out, so what is left is a shell that allows the IndexedDB API to easily sit on top of many different backends.

6. Serve as a playground for experimenting with IndexedDB.

License

Apache 2.0