localforage

What is localforage?

The localForage npm package is a fast and simple storage library for JavaScript. It improves the offline experience of web apps by using asynchronous storage (IndexedDB or WebSQL) with a simple, localStorage-like API. localForage uses a driver system that supports IndexedDB, WebSQL, and localStorage.

What are localforage's main functionalities?

Storing Data

This feature allows you to store data in the browser's asynchronous storage. The code sample demonstrates setting and then getting an item.

localforage.setItem('key', 'value').then(function () { return localforage.getItem('key'); }).then(function (value) { console.log(value); }).catch(function (err) { console.error(err); });

Retrieving Data

This feature allows you to retrieve data from the browser's asynchronous storage. The code sample demonstrates getting an item.

localforage.getItem('key').then(function (value) { console.log(value); }).catch(function (err) { console.error(err); });

Removing Data

This feature allows you to remove data from the browser's asynchronous storage. The code sample demonstrates removing an item.

localforage.removeItem('key').then(function () { console.log('Key is removed'); }).catch(function (err) { console.error(err); });

Clearing Storage

This feature allows you to clear all data from the browser's asynchronous storage. The code sample demonstrates clearing the storage.

localforage.clear().then(function () { console.log('Storage is now empty'); }).catch(function (err) { console.error(err); });

Iterating Over Keys

This feature allows you to iterate over all key-value pairs in the browser's asynchronous storage. The code sample demonstrates iterating over keys.

localforage.iterate(function (value, key, iterationNumber) { console.log([key, value]); }).then(function () { console.log('Iteration has completed'); }).catch(function (err) { console.error(err); });

Other packages similar to localforage

dexie

Dexie is a wrapper library for indexedDB, which is a low-level API for client-side storage of significant amounts of structured data. Dexie provides a more powerful query language than localForage and is designed to work with complex data structures.

pouchdb

PouchDB is an open-source JavaScript database inspired by Apache CouchDB that is designed to run well within the browser. PouchDB was created to help web developers build applications that work as well offline as they do online. It is more feature-rich than localForage, with synchronization capabilities.

idb-keyval

idb-keyval is a super-simple-small promise-based keyval store implemented with IndexedDB, providing a localStorage-like API. It is much smaller in size than localForage but does not have the same level of browser support or features.

README

localForage

localForage is a JavaScript library that improves the offline experience of your web app by using asynchronous storage (via IndexedDB or WebSQL where available) with a simple, localStorage-like API.

localForage uses localStorage in browsers with no IndexedDB or WebSQL support. Asynchronous storage is available in the current versions of all major browsers: Chrome, Firefox, IE, and Safari (including Safari Mobile). See below for detailed compatibility info.

To use localForage, just drop a single JavaScript file into your page:

<script src="localforage.js"></script>
<script>localforage.getItem('something', myCallback);</script>

Download the latest localForage from GitHub, or install with npm or bower:

npm install localforage
bower install localforage

localForage is compatible with browserify.

Supported Browsers/Platforms

localForage works in all modern browsers (IE 8 and above). Asynchronous storage is available in all browsers in bold, with localStorage fallback in parentheses.

• Android Browser 2.1
• Blackberry 7
• Chrome 23 (Chrome 4.0+ with localStorage)
• Chrome for Android 32
• Firefox 10 (Firefox 3.5+ with localStorage)
• Firefox for Android 25
• Firefox OS 1.0
• IE 10 (IE 8+ with localStorage)
• IE Mobile 10
• Opera 15 (Opera 10.5+ with localStorage)
• Opera Mobile 11
• Phonegap/Apache Cordova 1.2.0
• Safari 3.1 (includes Mobile Safari)

Different browsers have different storage limits, so plan accordingly.

Note that, thanks to WebSQL support, apps packaged with Phonegap will also use asynchronous storage. Pretty slick!

Support

Lost? Need help? Try the localForage API documentation.

If you're stuck using the library, running the tests, or want to contribute, to localForage, you can visit irc.mozilla.org and head to the #apps channel to ask questions about localForage.

The best person to ask about localForage is tofumatt, who is usually online from 8am-10pm Eastern Time.

How to use localForage

Callbacks

Because localForage uses async storage, it has an async API. It's otherwise exactly the same as the localStorage API.

// In localStorage, we would do:
localStorage.setItem('key', JSON.stringify('value'));
doSomethingElse();

// With localForage, we use callbacks:
localforage.setItem('key', 'value', doSomethingElse);

Similarly, please don't expect a return value from calls to localforage.getItem(). Instead, use a callback:

// Synchronous; slower!
var value = JSON.parse(localStorage.getItem('key'));
alert(value);

// Async, fast, and non-blocking!
localforage.getItem('key', alert);

Note that callbacks in localForage are Node-style (error argument first) since 0.9.3. This means if you're using callbacks, your code should look like this:

// Use err as your first argument.
localforage.getItem('key', function(err, value) {
    if (err) {
        console.error('Oh noes!');
    }

    alert(value);
});

You can store any type in localForage; you aren't limited to strings like in localStorage. Even if localStorage is your storage backend, localForage automatically does JSON.parse() and JSON.stringify() when getting/setting values.

Promises

Promises are pretty cool! If you'd rather use promises than callbacks, localForage supports that too:

function doSomethingElse(value) {
    console.log(value);
}

// With localForage, we allow promises:
localforage.setItem('key', 'value').then(doSomethingElse);

Note that with Promises, err is not the first argument to your function. Instead, you handle an error with the rejection part of the Promise:

// A full setItem() call with Promises.
localforage.setItem('key', 'value').then(function(value) {
    alert(value + ' was set!');
}, function(error) {
    console.error(error);
});

localForage relies on native ES6 Promises, but ships with an awesome polyfill for browsers that don't support ES6 Promises yet.

Storing Blobs, TypedArrays, and other JS objects

localForage supports storing all native JS objects that can be serialized to JSON, as well as ArrayBuffers, Blobs, and TypedArrays. Check the API docs for a full list of types supported by localForage.

All types are supported in every storage backend, though storage limits in localStorage make storing many large Blobs impossible.

Driver Selection (i.e. forcing localStorage)

For development, it can be easier to use the slower--but easier to debug--localStorage driver (mostly because localStorage can easily be inspected from the console). You can use the setDriver() method to change the driver localForage is using at any time.

// If you aren't using JS modules, things are loaded synchronously.
localforage.setDriver(localforage.LOCALSTORAGE);
alert(localforage.driver());
  => 'localStorageWrapper'

// If you're using modules, things load asynchronously, so you should use
// callbacks or promises to ensure things have loaded.
localforage.setDriver(localforage.LOCALSTORAGE, function() {
    alert(localforage.driver());
});
  => 'localStorageWrapper'

// The promises version:
localforage.setDriver(localforage.LOCALSTORAGE).then(function() {
    alert(localforage.driver());
});
  => 'localStorageWrapper'

You can actually force any available driver with this method, but given that the best driver will be selected automatically when the library is loaded, this method is mostly useful in forcing localStorage.

Note that trying to load a driver unavailable on the current browser (like trying to load WebSQL in Gecko) will fail and the previously loaded "best choice" will continue to be used.

Configuration

You can set database information, by giving the window.localForageConfig variable a hash of options. Available options are name, storeName, version, and description.

Example:

localforage.config({
    name        : 'myApp',
    version     : 1.0,
    size        : 4980736, // Size of database, in bytes. WebSQL-only for now.
    storeName   : 'keyvaluepairs', // Should be alphanumeric, with underscores.
    description : 'some description'
});

Note: you must call config() before you interact with your data. This means calling config() before using getItem(), setItem(), removeItem(), clear(), key(), keys() or length().

RequireJS

You can use localForage with RequireJS, and even though each driver will be loaded asynchronously with a require() call, you can use localForage without having to confirm that it's ready:

define(['localforage'], function(localforage) {
    // As a callback:
    localforage.setItem('mykey', 'myvalue', console.log);

    // With a Promise:
    localforage.setItem('mykey', 'myvalue').then(console.log);
});

In pre-1.0 versions you had to call .ready() to make sure the code was loaded, but this is no longer necessary.

Web Workers

Web Worker support in Firefox is blocked by bug 701634. Until it is fixed, web workers are not officially supported by localForage.

Framework Support

If you use a framework listed, there's a localForage storage driver for the models in your framework so you can store data offline with localForage. We have drivers for the following frameworks:

• AngularJS
• Backbone
• Ember

If you have a driver you'd like listed, please open an issue to have it added to this list.

Working on localForage

You'll need node/npm, bower, and Grunt.

To work on localForage, you should start by forking it and installing its dependencies. Replace USERNAME with your GitHub username and run the following:

git clone [e-mail]:USERNAME/localForage.git
cd localForage
npm install
bower install

Omitting the bower dependencies will cause the tests to fail!

Running Tests

You need PhantomJS installed to run local tests. Run npm test (or, directly: grunt test). Your code must also pass the linter.

localForage is designed to run in the browser, so the tests explicitly require a browser environment. Local tests are run on a headless WebKit (using PhantomJS), but cross-browser tests are run using Sauce Labs.

If you have Sauce Labs credentials on your machine, localForage will attempt to connect to Sauce Labs to run the tests on Sauce Labs as well. To skip Sauce Labs tests, run grunt test:local.

When you submit a pull request, tests will be run against all browsers that localForage supports.

License

This program is free software; it is distributed under an Apache License.

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Copyright (c) 2013-2014 Mozilla (Contributors).

Changelog

1.1

• Custom drivers can be created using defineDriver(). (#282; fixes #267)