localForage

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

localForage includes a localStorage-backed fallback store for 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 bower:

bower install localforage

Supported Browsers/Platforms

localForage works in all modern browsers (IE 8 and above). Asynchronous storage is available in all browsers in bold, with their version that supports localStorage 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)

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

Support

Lost? Need help? This README has some simple guides and the code has decent documentation, but I'm working on a real API guide. In the meantime, if you're stuck using the library, running the tests, or want to contribute, you can visit irc.mozilla.org and head to the #apps channel to ask questions about localForage.

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);

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);

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

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('localStorageWrapper');
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('localStorageWrapper', function() {
    alert(localforage.driver);
});
  => 'localStorageWrapper'

// The promises version:
localforage.setDriver('localStorageWrapper').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:

window.localForageConfig = {
    name        : 'myApp',
    version     : 1.0,
    size        : 4980736, // Size of database, in bytes. WebSQL-only for now.
    storeName   : 'keyvaluepairs',
    description : 'some description'
};

RequireJS

You can use localForage with RequireJS, but note that because of the way drivers are loaded using RequireJS, you'll want to make sure localforage.ready's Promise has been fulfilled to ensure all of localForage is ready to use before you make set/get calls. Essentially, to use localForage with RequireJS, your code should look like this:

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

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

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

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 git@github.com:USERNAME/localForage.git
cd localForage
npm install
bower install

Omitting the bower dependencies will cause the tests to fail!

Running Tests

tl;dr: You need PhantomJS and SlimerJS installed to run tests. Then, just run npm test (or, directly, grunt test). Your code must also pass the linter.

Note for Windows users: SlimerJS doesn't seem to work on Windows for our tests, so run the tests with grunt test --force. The SlimerJS versions will be run on Travis when you submit a pull request.

localForage is designed to run in the browser, so the tests explicitly require a browser environment instead of any JavaScript environment (i.e. node.js). The tests are run on both a headless WebKit (using PhantomJS) and "headless" Gecko (using SlimerJS). The tests are written using CasperJS's tester module. We run tests against Gecko and WebKit to ensure that IndexedDB and WebSQL support is functioning as-expected.

On Mac OS X, you'll need to install both PhantomJS and SlimerJS like so:

brew install phantomjs slimerjs

If you're using Windows or Linux, you can get get PhantomJS and get SlimerJS from their websites. I haven't tried it myself, but it seems easy enough.

Generally you'll need a version of Firefox or XULRunner installed for SlimerJS to run your tests. The exact steps how to install and setup SlimerJS are described on the project homepage.

Once everything is installed you can simply type grunt test to make sure the code is working as expected. This will also check your code quality, ensuring your patch is in-line with localForage's code style.

TODO: Provide Windows/Linux instructions; check into XULRunner setup.

Frequently Asked Questions

Will you add (or accept) support for X storage?

Maybe. If it's legacy storage (< IE 8), for a dead platform (WebOS), or really obscure (Apple Newton), I'm going to say "no". If it's for a new browser technology or a platform-specific driver like Chrome Web Apps or Firefox OS, then "yes" is probably the answer.

Will you add support for node.js?

No. This is a library focused on offline storage inside a web browser. Node.js already has lots of storage solutions. The problem this library aims to solve is that web browsers differ greatly in their support for a common API for dealing with the same kind of data. Node.js doesn't have that problem; if you want to use an API, you just add a library to your package.json.

License

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

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