idb-keyval/README.md

# IDB-Keyval

[![npm](https://img.shields.io/npm/v/idb-keyval.svg)](https://www.npmjs.com/package/idb-keyval)

This is a super-simple promise-based keyval store implemented with IndexedDB, originally based on [async-storage by Mozilla](https://github.com/mozilla-b2g/gaia/blob/master/shared/js/async_storage.js).

It's small and tree-shakeable. If you only use get/set, the library is ~370 bytes (brotli'd), if you use all methods it's ~570 bytes.

Although this is tiny, it's a little larger than previous versions due to a [massive bug in Safari](https://bugs.webkit.org/show_bug.cgi?id=226547). Hopefully this fix can be removed in the not-too-distant future, when a version of Safari without the bug reaches enough users.

[localForage](https://github.com/localForage/localForage) offers similar functionality, but supports older browsers with broken/absent IDB implementations. Because of that, it's orders of magnitude bigger (~7k).

This is only a keyval store. If you need to do more complex things like iteration & indexing, check out [IDB on NPM](https://www.npmjs.com/package/idb) (a little heavier at 1k). The first example in its README is how to create a keyval store.

## Installing

### Recommended: Via npm + webpack/rollup/parcel/etc

```sh
npm install idb-keyval
```

Now you can require/import `idb-keyval`:

```js
import { get, set } from 'idb-keyval';
```

If you're targeting IE10/11, use the compat version, and import a `Promise` polyfill.

```js
// Import a Promise polyfill
import 'es6-promise/auto';
import { get, set } from 'idb-keyval/dist/esm-compat';
```

### All bundles

A well-behaved bundler should automatically pick the ES module or the CJS module depending on what it supports, but if you need to force it either way:

- `idb-keyval/dist/index.js` EcmaScript module.
- `idb-keyval/dist/index.cjs` CommonJS module.

Legacy builds:

- `idb-keyval/dist/compat.js` EcmaScript module, transpiled for older browsers.
- `idb-keyval/dist/compat.cjs` CommonJS module, transpiled for older browsers.
- `idb-keyval/dist/umd.js` UMD module, also transpiled for older browsers.

These built versions are also available on jsDelivr, e.g.:

```html
<script src="https://cdn.jsdelivr.net/npm/idb-keyval@6/dist/umd.js"></script>
<!-- Or in modern browsers: -->
<script type="module">
  import { get, set } from 'https://cdn.jsdelivr.net/npm/idb-keyval@6/+esm';
</script>
```

## Usage

### set:

```js
import { set } from 'idb-keyval';

set('hello', 'world');
```

Since this is IDB-backed, you can store anything structured-clonable (numbers, arrays, objects, dates, blobs etc), although old Edge doesn't support `null`. Keys can be numbers, strings, `Date`s, (IDB also allows arrays of those values, but IE doesn't support it).

All methods return promises:

```js
import { set } from 'idb-keyval';

set('hello', 'world')
  .then(() => console.log('It worked!'))
  .catch((err) => console.log('It failed!', err));
```

### get:

```js
import { get } from 'idb-keyval';

// logs: "world"
get('hello').then((val) => console.log(val));
```

If there is no 'hello' key, then `val` will be `undefined`.

### setMany:

Set many keyval pairs at once. This is faster than calling `set` multiple times.

```js
import { set, setMany } from 'idb-keyval';

// Instead of:
Promise.all([set(123, 456), set('hello', 'world')])
  .then(() => console.log('It worked!'))
  .catch((err) => console.log('It failed!', err));

// It's faster to do:
setMany([
  [123, 456],
  ['hello', 'world'],
])
  .then(() => console.log('It worked!'))
  .catch((err) => console.log('It failed!', err));
```

This operation is also atomic – if one of the pairs can't be added, none will be added.

### getMany:

Get many keys at once. This is faster than calling `get` multiple times. Resolves with an array of values.

```js
import { get, getMany } from 'idb-keyval';

// Instead of:
Promise.all([get(123), get('hello')]).then(([firstVal, secondVal]) =>
  console.log(firstVal, secondVal),
);

// It's faster to do:
getMany([123, 'hello']).then(([firstVal, secondVal]) =>
  console.log(firstVal, secondVal),
);
```

### update:

Transforming a value (eg incrementing a number) using `get` and `set` is risky, as both `get` and `set` are async and non-atomic:

```js
// Don't do this:
import { get, set } from 'idb-keyval';

get('counter').then((val) =>
  set('counter', (val || 0) + 1);
);

get('counter').then((val) =>
  set('counter', (val || 0) + 1);
);
```

With the above, both `get` operations will complete first, each returning `undefined`, then each set operation will be setting `1`. You could fix the above by queuing the second `get` on the first `set`, but that isn't always feasible across multiple pieces of code. Instead:

```js
// Instead:
import { update } from 'idb-keyval';

update('counter', (val) => (val || 0) + 1);
update('counter', (val) => (val || 0) + 1);
```

This will queue the updates automatically, so the first `update` set the `counter` to `1`, and the second `update` sets it to `2`.

### del:

Delete a particular key from the store.

```js
import { del } from 'idb-keyval';

del('hello');
```

### delMany:

Delete many keys at once. This is faster than calling `del` multiple times.

```js
import { del, delMany } from 'idb-keyval';

// Instead of:
Promise.all([del(123), del('hello')])
  .then(() => console.log('It worked!'))
  .catch((err) => console.log('It failed!', err));

// It's faster to do:
delMany([123, 'hello'])
  .then(() => console.log('It worked!'))
  .catch((err) => console.log('It failed!', err));
```

### clear:

Clear all values in the store.

```js
import { clear } from 'idb-keyval';

clear();
```

### entries:

Get all entries in the store. Each entry is an array of `[key, value]`.

```js
import { entries } from 'idb-keyval';

// logs: [[123, 456], ['hello', 'world']]
entries().then((entries) => console.log(entries));
```

### keys:

Get all keys in the store.

```js
import { keys } from 'idb-keyval';

// logs: [123, 'hello']
keys().then((keys) => console.log(keys));
```

### values:

Get all values in the store.

```js
import { values } from 'idb-keyval';

// logs: [456, 'world']
values().then((values) => console.log(values));
```

### Custom stores:

By default, the methods above use an IndexedDB database named `keyval-store` and an object store named `keyval`. If you want to use something different, see [custom stores](./custom-stores.md).