use-broadcast-ts

Use the Broadcast Channel API in React easily with hooks or Zustand, and Typescript!

npm install use-broadcast-ts

This package allows you to use the Broadcast API with a simple hook or by using Zustand v4/v5.

Checkout the demo!

Usage with Zustand

// useStore.ts
import { create } from 'zustand';
import { shared } from 'use-broadcast-ts';

type MyStore = {
    count: number;
    set: (n: number) => void;
};

const useStore = create<MyStore>(
    shared(
        (set) => ({
            count: 0,
            set: (n) => set({ count: n })
        }),
        { name: 'my-channel' }
    )
);

// MyComponent.tsx
import { FC } from 'react';
import { useShallow } from 'zustand/shallow'

const MyComponent : FC = () => {

    const count = useStore((s) => s.count);
    const set = useStore((s) => s.set);

    return (
        <p>
            <p>Count: {count}</p>
            <button onClick={() => set(10)}/>
        </p>
    )
}

export default MyComponent;

You can use the Zustand store like any other Zustand store, but the store will be shared between all the tabs.

On the first "render" of the store, the middleware will check if the store already exists in another tab / window. If the store exits, it will be synchronized, else the store will be created.

If no tab is opened, the store will be created and will be shared as the "main" with the other tabs / windows.

Note: It cannot be used in server components as it needs an environment that support the Broadcast Channel API

New in v1.4.0

• You don't have to specify a channel name anymore. The channel name is now automatically generated. However, I strongly recommend you to use it.

Usage with hooks

import { FC } from 'react';
import { useBroadcast } from 'use-broadcast-ts';

const MyComponent: FC = () => {
    const { state, send } = useBroadcast<{ value: number }>('my-channel', { value: 0 });

    return (
        <>
            <p>My value is: {state.value}</p>
            <button onClick={() => send({ value: 10 })} />
        </>
    );
};

export default MyComponent;

With the example above, the component will re-render when the channel receive or send a value.

import { FC, useEffect } from 'react';
import { useBroadcast } from 'use-broadcast-ts';

const MyComponent: FC = () => {
    const { send, subscribe } = useBroadcast<{ value: number }>('my-channel', { value: 0 }, { subscribe: true });

    useEffect(() => {
	    const unsub = subscribe(({ value }) => console.log(`My new value is: ${value}`));

	    return () => unsub();
    }, []);

    return (
        <>
            <button onClick={() => send({ value: 10 })} />
        </>
    );
};

export default MyComponent;

With the example above, the component will not re-render when the channel receive or send a value but will call the subscribe callback.

API

shared (Zustand)

    shared(
        (set, get, ...) => ...,
        options?: SharedOptions
    );

Parameters

options

Type: SharedOptions

The options of the hook.

options.name

Type: string

The name of the channel to use.

options.mainTimeout

Type: number (default: 100)

The timeout in ms to wait for the main tab to respond.

options.unsync

Type: boolean (default: false)

If true, the store will only synchronize once with the main tab. After that, the store will be unsynchronized.

options.skipSerialization

Type: boolean (default false)

If true, will not serialize the state with JSON.parse(JSON.stringify(state)) before sending it. This results in a performance boost, but you will have to ensure there are no unsupported types in the state or it will result in errors. See section What data can I send? for more info.

options.partialize

Type: (state: T) => Partial<T> (default: undefined)

Similar to partialize in the Zustand persist middleware, allows you to pick which of the state's fields are sent to other tabs. Can also be used to pre-process the state before it's sent if needed.

options.merge

Type: (state: T, receivedState: Partial<T>) => T (default: undefined)

Similar to merge in the Zustand persist middleware. A custom function that allows you to merge the current state with the state received from another tab.

options.onBecomeMain

Type: (id: number) => void

A callback that will be called when the tab becomes the main tab.

options.onTabsChange

Type: (tabs: number[]) => void

A callback that will be called when the number of tabs changes. Only triggered on the main tab.

useBroadcast (hooks)

useBroadcast<T>(name: string, value?: T, options?: UseBroadcastOptions): {
    state: T;
    send: (value: T) => void;
    subscribe: (callback: (e: T) => void) => () => void;
};

Parameters

name

Type: string

The name of the channel to use.

value

Type: T (default: undefined)

The initial value of the channel.

options

Type: UseBroadcastOptions (default: {})

The options of the hook.

options.subscribe

Type: boolean | undefined (default: undefined)

If true, the hook will not re-render the component when the channel receive a new value but will call the subscribe callback.

Return

state

Type: T

The current value of the channel.

send

Type: (value: T) => void

Send a new value to the channel.

subscribe

Type: (callback: (e: T) => void) => () => void

Subscribe to the channel. The callback will be called when the channel receive a new value and when the options.subscribe is set to true.

What data can I send?

You can send any of the supported types by the structured clone algorithm and JSON.stringify like :

• String
• Boolean
• Number
• Array
• Object
• Date
• ...

In short, you cannot send :

• Function
• Dom Element
• BigInt (This is only unsupported by JSON.stringify, so if you set skipSerialization=true, BigInt's will work)
• And some other types

See the MDN documentation for more information. However, if you need to, you could use partialize to convert an unsupported type to a string and convert it back on the other end by providing a merge function.

License

MIT