@rehooks/local-storage

React hook for enabling synchronization with local-storage.

API Docs can be found here.

Table of Contents

• @rehooks/local-storage
  • Table of Contents
  • Features
  • Install
    • With Yarn
    • With NPM
  • Usage
    • Write to Storage
    • Read From Storage
      • Optionally use a default value
    • Delete From Storage
    • Using With Context
  • Full Example
  • Contributors ✨

Features

• Automatic JSON serialization
• Synchronization across multiple tabs
• Provides functions for updating the localStorage and triggering a state update outside of the component
• Type hinting via TypeScript

Install

With Yarn

yarn add @rehooks/local-storage

With NPM

npm i @rehooks/local-storage --save

Usage

Write to Storage

This can be anywhere from within your application.

Note: Objects that are passed to writeStorage are automatically stringified. This will not work for circular structures.

import React from 'react';
import { writeStorage } from '@rehooks/local-storage';

let counter = 0;

const MyButton = () => (
  <button onClick={_ => writeStorage('i', ++counter)}>
    Click Me
  </button>
);

Read From Storage

This component will receive updates to itself from local storage.

Javascript:

import React from 'react';
import { useLocalStorage } from '@rehooks/local-storage';

function MyComponent() {
  const [counterValue] = useLocalStorage('i'); // send the key to be tracked.
  return (
    <div>
      <h1>{counterValue}</h1>
    </div>
  );
}

Typescript:

import React from 'react';
import { useLocalStorage } from '@rehooks/local-storage';

function MyComponent() {
  const [counterValue] = useLocalStorage<number>('i'); // specify a type argument for your type
  // Note: Since there was no default value provided, this is potentially null.
  return (
    <div>
      <h1>{counterValue}</h1>
    </div>
  );
}

Optionally use a default value

Note: Objects that are passed to useLocalStorage's default parameter will be automatically stringified. This will not work for circular structures.

import React from 'react';
import { useLocalStorage } from '@rehooks/local-storage';

function MyComponent() {
  // Note: The type of user can be inferred from the default value type
  const [user] = useLocalStorage('user', { name: 'Anakin Skywalker' });
  return (
    <div>
      <h1>{user.name}</h1>
    </div>
  );
}

Delete From Storage

You may also delete items from the local storage as well.

import { writeStorage, deleteFromStorage } from '@rehooks/local-storage';

writeStorage('name', 'Homer Simpson'); // Add an item first

deleteFromStorage('name'); // Deletes the item

const thisIsNull = localStorage.getItem('name'); // This is indeed null

Using With Context

It is advisable to use this hook with context if you want to have a properly synchronized default value. Using useLocalStorage in two different components with the same key but different default values can lead to unexpected behaviour.

Using Context will also prevent components from rendering and setting default values to the localStorage when you just want them to be deleted from localStorage (assuming the context provider also does not re-render).

import React, { createContext, useContext } from 'react';
import { useLocalStorage } from '@rehooks/local-storage';

const defaultProfile = { name: 'Spongekebob' };
const defaultContextValue = [defaultProfile, () => {}, () => {}];

const ProfileContext = createContext(defaultContextValue);

export const ProfileProvider = ({ children }) => {
  const ctxValue = useLocalStorage('profile', defaultProfile);
  return (
    <ProfileContext.Provider value={ctxValue}>
      {children}
    </ProfileContext.Provider>
  );
};

const useProfile = () => useContext(ProfileContext);

const App = () => {
  const [profile] = useProfile();
  return <h1>{profile && profile.name}</h1>;
};

export default () => {
  return (
    <ProfileProvider>
      <App />
    </ProfileProvider>
  );
};

Full Example

You may view this example here on StackBlitz.

Note: The writeStorage and deleteFromStorage functions are provided from useLocalStorage as well, and do not require you to specify the key when using them.

import React, { Fragment } from 'react';
import { render } from 'react-dom';
import { writeStorage, deleteFromStorage, useLocalStorage } from '@rehooks/local-storage';

const startingNum = 0;

const Clicker = () => (
  <Fragment>
    <h4>Clicker</h4>
    <button onClick={_ => {
      writeStorage('num', localStorage.getItem('num')
      ? +(localStorage.getItem('num')) + 1
      : startingNum
      )
    }}>
      Increment From Outside
    </button>
    <button onClick={_ => deleteFromStorage('num')}>
      Delete From Outside
    </button>
  </Fragment>
);

const IncrememterWithButtons = () => {
  const [number, setNum, deleteNum] = useLocalStorage('num');

  return (
    <Fragment>
      <p>{typeof(number) === 'number' ? number : 'Try incrementing the number!'}</p>
      <button onClick={_ => setNum(number !== null ? +(number) + 1 : startingNum)}>Increment</button>
      <button onClick={deleteNum}>Delete</button>
    </Fragment>
  );
};

const App = () => (
  <Fragment>
    <h1> Demo </h1>
    <IncrememterWithButtons />
    <Clicker />
  </Fragment>
);

// Assuming there is a div in index.html with an ID of 'root'
render(<App />, document.getElementById('root'));

Contributors ✨

Thanks goes to these wonderful people (emoji key):

This project follows the all-contributors specification. Contributions of any kind welcome!