This is a super-simple promise-based keyval store implemented with IndexedDB, originally based on async-storage by Mozilla.

It's small and tree-shakeable. If you only use get/set, the library is ~250 bytes (brotli'd), if you use all methods it's ~534 bytes.

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 (a little heavier at 1k). The first example in its README is how to create a keyval store.

npm install idb-keyval

Now you can require/import idb-keyval:

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

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

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

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.:

<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>

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, Dates, (IDB also allows arrays of those values, but IE doesn't support it).

All methods return promises:

import { set } from 'idb-keyval';

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

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.

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

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.

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

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),
);

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

// 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:

// 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.

Delete a particular key from the store.

import { del } from 'idb-keyval';

del('hello');

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

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 all values in the store.

import { clear } from 'idb-keyval';

clear();

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

import { entries } from 'idb-keyval';

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

Get all keys in the store.

import { keys } from 'idb-keyval';

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

Get all values in the store.

import { values } from 'idb-keyval';

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

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.