Manage Chrome Extension storage easily with @extend-chrome/storage.

This is a wrapper for the Chrome Extension Storage API that adds great TypeScript support using virtual storage buckets with a modern Promise-based API.

Table of Contents

• Getting Started
• Usage
• Features
• API
  • interface Bucket
    • bucket.get()
    • bucket.getKeys()
    • bucket.set()
    • bucket.remove()
    • bucket.clear()
    • bucket.changeStream
    • bucket.valueStream
  • function getBucket()

Getting started

You will need to use a bundler like Rollup, Parcel, or Webpack to include this library in your Chrome extension.

See rollup-plugin-chrome-extension for an easy way to use Rollup to build your Chrome extension!

Installation

npm i @extend-chrome/storage

Usage

Add the storage permission to your manifest.json file.

// manifest.json
{
  "permissions": ["storage"]
}

Take your Chrome extension to another level! 🚀

import { storage } from '@extend-chrome/storage'

// Set storage using an object
storage.set({ friends: ['Jack'] })

// Set storage using a function
storage.set(({ friends }) => {
  // friends is ['Jack']
  return { friends: [...friends, 'Amy'] }
})

// Get storage value using a key
storage.get('friends').then(({ friends }) => {
  // friends is ['Jack', 'Amy']
})

// Get storage values using an object
storage
  .get({ friends: [], enemies: [] })
  .then(({ friends, enemies }) => {
    // friends is ['Jack', 'Amy']
    // enemies is the [] from the getter object
  })

Features

Virtual typed storage buckets

This library allows you to create a storage area and define the type of data that area will manage.

import { getBucket } from '@extend-chrome/storage'

interface Store {
  a: string
  b: number
}

const store = getBucket<Store>('store')

store.set({ a: 'abc', b })
store.set(({ b = 0 }) => ({ b: b + 500 }))

store.set({ c: true }) // ts error
store.set(({ a }) => ({ d: 'invalid' })) // ts error

Promises and functional setters

The Chrome Storage API is asynchronous. This means synchronous calls to get and set will not reflect pending changes. This makes calls to set that depend on values held in storage difficult.

While the Chrome Storage API is async, it uses callbacks. This brings a whole world of difficulty into the developer experience that have been solved with Promises.

@extend-chrome/storage solves both of these problems. Every method returns a Promise and both get and set can take a function that provides current storage values, similar to React's this.setState.

Composed set operations

The set method can be called with a function (setter) as well as the normal types (a string, array of strings, or an object).

This setter will receive the entire contents of that storage area as an argument. It must return an object which will be passed to the native storage area set method.

Synchronous calls to set will be composed into one call to the native set. The setters will be applied in order, but each call will resolve with the final value passed to the storage area.

bucket.set({ a: 123 })
bucket.set({ b: 456 })
bucket
  .set(({ a, b }) => {
    // a === 123
    // b === 456
    return { c: 789 }
  })
  .then(({ a, b, c }) => {
    // New values in bucket
    // a === 123
    // b === 456
    // c === 789
  })

An individual call to set will reject if the setter function throws an error or returns an invalid type, but will not affect other set operations.

API

interface Bucket

A synthetic storage area. It has the same methods as the native Chrome API StorageArea, but get and set can take a function as an argument. A Bucket can use either local or sync storage.

Multiple synchronous calls to set are composed into one call to the native Chrome API StorageArea.set.

Create a bucket or two using getBucket:

import { getBucket } from '@extend-chrome/storage'

// Buckets are isomorphic, so export and
// use them throughout your extension
export const bucket1 = getBucket('bucket1')
export const bucket2 = getBucket('bucket2')

Each bucket is separate, so values don't overlap.

bucket1.set({ a: 123 })
bucket2.set({ a: 'abc' })

bucket1.get() // { a: 123 }
bucket2.get() // { a: 'abc' }

Buckets really shine if you're using TypeScript, because you can define the types your bucket will contain. Click here for more details.

async function bucket.get

Takes an optional getter. Resolves to an object with the requested storage area values.

function get(getter?: string | object | Function) => Promise<{ [key: string]: any }>

[getter]
Type: null, string, string array, or function
Default: null
Usage is the same as for the native Chrome API, except for the function getter.

• Use null to get the entire bucket contents.
• Use a string as a storage area key to get an object with only that key/value pair.
• Use an object with property names for the storage keys you want.
  • The values for each property will be used if the key is undefined in storage.
• Use a function to map the contents of storage to any value.
  • The function will receive the entire contents of storage as the first argument.
  • The call to get will resolve to the function's return value.
• Calls to get after set will resolve to the new set values.

bucket.get('a') // resolves to object as key/value pair
bucket.get({ a: 123 }) // same, but 123 is default value
bucket.get(({ a }) => a) // resolves to value of "a"

async function bucket.getKeys

Takes no arguments. Resolves to an array of strings that represents the keys of the values in the storage area bucket.

function getKeys() => Promise<string[]>

bucket.set({ a: 123 })
bucket.getKeys() // Resolves to ['a']

async function bucket.set

Set a value or values in storage. Takes a setter object or function. Resolves to the new bucket values.

function set(setter: object | Function) => Promise<{ [key: string]: any }>

setter
Type: object or Function

• Use an object with key/value pairs to set those values to storage.
• Use a Function that returns an object with key/value pairs.
  • The setter function receives the results of previous synchronous set operations.
  • The setter function cannot be an async function.
• Returns a Promise that resolves to the new storage values.
• Calls to get after set will resolve with the new values.

// Values in bucket: { a: 'abc' }

// First call to set
bucket.set({ b: 123 })

// Second synchronous call to set
bucket
  .set(({ a, b, c }) => {
    // Values composed from storage
    // and previous call to set:
    // a === 'abc'
    // b === 123
    // c === undefined
    return { c: true }
  })
  .then(({ a, b, c }) => {
    // New values in storage
    // a === 'abc'
    // b === 123
    // c === true
  })

bucket.set({ a: 123 })
bucket
  .set(({ a }) => ({ b: true }))
  .then(({ a, b }) => {
    // Values were set
    // a === 123
    // b === true
  })

async function bucket.remove

Remove a value or values from storage. Resolves when the operation is complete.

bucket.remove('a')
bucket.remove(['a', 'b'])

async function bucket.clear

Empties only this bucket. Resolves when the operation is complete. Other buckets are untouched.

bucket.clear()

async function bucket.changeStream

An RxJs Observable that emits a StorageChange object when the Chrome Storage API onChanged event fires.

bucket.changeStream
  .pipe(filter(({ a }) => !!a))
  .subscribe(({ a }) => {
    console.log('old value', a.oldValue)
    console.log('new value', a.newValue)
  })

async function bucket.valueStream

An Observable that emits all the values in storage immediately, and when onChanged fires.

bucket.valueStream.subscribe((values) => {
  console.log('Everything in this bucket', values)
})

function getBucket

Create a bucket (a synthetic storage area). Takes a string bucketName and an optional string areaName. Returns a Bucket synthetic storage area. Export this bucket and use it throughout your Chrome extension. It will work everywhere, including privileged pages and content scripts.

getBucket is a TypeScript Generic. Pass it an interface to define the types to expect in your storage area.

function getBucket(bucketName: string, areaName?: 'local' | 'sync') => Bucket

bucketName
Type: string
A unique id for this bucket.

[areaName]
Type: "local" or "sync"
Default: "local"
Choose which native Chrome API storage area to use.

import { getBucket } from '@extend-chrome/storage'

// JavaScript
export const localBucket = getBucket('bucket1')
export const syncBucket = getBucket('bucket2', 'sync')

// TypeScript
export const localBucket = getBucket<{ a: string }>('bucket1')
export const syncBucket = getBucket<{ b: number }>(
  'bucket2',
  'sync',
)