# localForage
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localForage is a fast and simple storage library for JavaScript. localForage
improves the offline experience of your web app by using asynchronous storage
(IndexedDB or WebSQL) with a simple, `localStorage`-like API.

localForage uses localStorage in browsers with no IndexedDB or
WebSQL support. See [the wiki for detailed compatibility info][supported browsers].

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

```html
<script src="localforage/dist/localforage.js"></script>
<script>localforage.getItem('something', myCallback);</script>
```
Try the [live example](http://codepen.io/thgreasi/pen/ojYKeE).

Download the [latest localForage from GitHub](https://github.com/localForage/localForage/releases/latest), or install with
[npm](https://www.npmjs.com/):

```bash
npm install localforage
```

[supported browsers]: https://github.com/localForage/localForage/wiki/Supported-Browsers-Platforms

## Support

Lost? Need help? Try the
[localForage API documentation](https://localforage.github.io/localForage). [localForage API文档也有中文版。](https://localforage.docschina.org)

If you're having trouble using the library, running the tests, or want to contribute to localForage, please look through the [existing issues](https://github.com/localForage/localForage/issues) for your problem first before creating a new one. If you still need help, [feel free to file an issue](https://github.com/localForage/localForage/issues/new).

# How to use localForage

## Callbacks vs Promises

Because localForage uses async storage, it has an async API.
It's otherwise exactly the same as the
[localStorage API](https://hacks.mozilla.org/2009/06/localstorage/).

localForage has a dual API that allows you to either use Node-style callbacks
or [Promises](https://www.promisejs.org/). If you are unsure which one is right for you, it's recommended to use Promises.

Here's an example of the Node-style callback form:

```js
localforage.setItem('key', 'value', function (err) {
  // if err is non-null, we got an error
  localforage.getItem('key', function (err, value) {
    // if err is non-null, we got an error. otherwise, value is the value
  });
});
```

And the Promise form:

```js
localforage.setItem('key', 'value').then(function () {
  return localforage.getItem('key');
}).then(function (value) {
  // we got our value
}).catch(function (err) {
  // we got an error
});
```

Or, use `async`/`await`:

```js
try {
    const value = await localforage.getItem('somekey');
    // This code runs once the value has been loaded
    // from the offline store.
    console.log(value);
} catch (err) {
    // This code runs if there were any errors.
    console.log(err);
}
```

For more examples, please visit [the API docs](https://localforage.github.io/localForage).

## Storing Blobs, TypedArrays, and other JS objects

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.

localForage supports storing all native JS objects that can be serialized to
JSON, as well as ArrayBuffers, Blobs, and TypedArrays. Check the
[API docs][api] 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.

[api]: https://localforage.github.io/localForage/#data-api-setitem

## Configuration

You can set database information with the `config()` method.
Available options are `driver`, `name`, `storeName`, `version`, `size`, and
`description`.

Example:
```javascript
localforage.config({
    driver      : localforage.WEBSQL, // Force WebSQL; same as using setDriver()
    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()`.

## Multiple instances

You can create multiple instances of localForage that point to different stores
using `createInstance`. All the configuration options used by
[`config`](#configuration) are supported.

``` javascript
var store = localforage.createInstance({
  name: "nameHere"
});

var otherStore = localforage.createInstance({
  name: "otherName"
});

// Setting the key on one of these doesn't affect the other.
store.setItem("key", "value");
otherStore.setItem("key", "value2");
```

## RequireJS

You can use localForage with [RequireJS](http://requirejs.org/):

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

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

## TypeScript

If you have the [`allowSyntheticDefaultImports` compiler option](https://www.typescriptlang.org/docs/handbook/compiler-options.html) set to `true` in your [tsconfig.json](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) (supported in TypeScript v1.8+), you should use:

```javascript
import localForage from "localforage";
```

Otherwise you should use one of the following:

```javascript
import * as localForage from "localforage";
// or, in case that the typescript version that you are using
// doesn't support ES6 style imports for UMD modules like localForage
import localForage = require("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](https://github.com/ocombe/angular-localForage)
* [Angular 4 and up](https://github.com/Alorel/ngforage/)
* [Backbone](https://github.com/localForage/localForage-backbone)
* [Ember](https://github.com/genkgo/ember-localforage-adapter)
* [Vue](https://github.com/dmlzj/vlf)
* [NuxtJS](https://github.com/nuxt-community/localforage-module)

If you have a driver you'd like listed, please
[open an issue](https://github.com/localForage/localForage/issues/new) to have it
added to this list.

## Custom Drivers

You can create your own driver if you want; see the
[`defineDriver`](https://localforage.github.io/localForage/#driver-api-definedriver) API docs.

There is a [list of custom drivers on the wiki][custom drivers].

[custom drivers]: https://github.com/localForage/localForage/wiki/Custom-Drivers

# Working on localForage

You'll need [node/npm](http://nodejs.org/) and
[bower](http://bower.io/#installing-bower).

To work on localForage, you should start by
[forking it](https://github.com/localForage/localForage/fork) and installing its
dependencies. Replace `USERNAME` with your GitHub username and run the
following:

```bash
# Install bower globally if you don't have it:
npm install -g bower

# Replace USERNAME with your GitHub username:
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

You need PhantomJS installed to run local tests. Run `npm test` (or,
directly: `grunt test`). Your code must also pass the
[linter](http://jshint.com/).

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](http://phantomjs.org)).

When you submit a pull request, tests will be run against all browsers that
localForage supports on Travis CI using [Sauce Labs](https://saucelabs.com/).

## Library Size
As of version 1.7.3 the payload added to your app is rather small. Served using gzip compression, localForage will add less than 10k to your total bundle size:

<dl>
  <dt>minified</dt><dd>`~29kB`</dd>
  <dt>gzipped</dt><dd>`~8.8kB`</dd>
  <dt>brotli'd</dt><dd>`~7.8kB`</dd>
</dl>

# License

This program is free software; it is distributed under an
[Apache License](https://github.com/localForage/localForage/blob/master/LICENSE).

---

Copyright (c) 2013-2016 [Mozilla](https://mozilla.org)
([Contributors](https://github.com/localForage/localForage/graphs/contributors)).
