Key features

• Module augmentation to reuse your types that are on a backend. More on that here
• TypeScript support
• Reusable React.js hooks

Installation

• With yarn

  yarn add use-socket-io-react

• With npm

  npm install use-socket-io-react

Setup

Wrap the application with a SocketProvider. For example, with React 18 it can be done like so:

const SERVER_URI = 'http://localhost:4000';

ReactDOM.render(
  <SocketProvider uri={SERVER_UR}>
    <App />
  </SocketProvider>,
  document.getElementById('root'),
);

The URI prop needs to point to a backend server. Don't forget about handling a CORS policy on a server because since version 3 of a socket.io it needs to be set explicitly.

Handling events

There is a hook called useSocketEvent. As a first argument, it takes an event name and in a resolution, it returns an object with a data array. Values in an array match to an order in which values are passed to an io.emit on a server.

// Server
io.emit('alert', 'Hey, you are the best!');

// Client
const {
  data: [alert],
} = useSocketEvent<[string]>('alert');

if (alert) {
  return <p>You received an alert: ${alert}</p>;
}

Alternatively useSocketEvent provides a handler callback that gets dispatched when the socket receives an event.

// Server
io.emit('chat', 'Hello John!', '12:38');

// Client
const [messages, setMessages] = useState<
  Array<{ message: string; sentAt: string }>
>([]);

const handleMessage = ([message, sentAt]: [string, string]) => {
  setMessages([...messages, { message: message, sentAt: sentAt }]);
};

useSocketEvent<[string, string]>('chat', {
  handler: handleMessage,
});

return (
  <section>
    {messages.map(({ message, sentAt }) => (
      <p>
        {message} ({sentAt})
      </p>
    ))}
  </section>
);

Emitting events

For emitting there is a hook called useSocketEmit. It doesn't take any argument but it returns an emit function.

const { emit } = useSocketEmit();

emit<[string]>('message', ['Hey, this is my message']);

You can provide a generic of how your emitted values need to look, but that's not recommended. Take a look at module augmentation

Socket state

Hook called useSocket stores values about a current socket state. It knows e.g. if a socket is either connected or there is some error.

const {
  socket,
  status,
  isConnected,
  isConnecting,
  isDisconnected,
  disconnectReason,
  isError,
  error,
} = useSocket();

// Or you can check: status === 'error'
if (isError) {
  return <p>Error! {error}</p>;
}

if (isDisconnected) {
  return <p>Socket disconnected {disconnectReason}</p>;
}

if (isConnecting) {
  return <p>Is loading</p>;
}

In addition, useSocket returns a native socket from a socket.io-client if some feature is needed that's currently beyond this library.

Socket.io introduces TypeScript support. This library supports this idea too. It's possible to abandon passing generic to every useSocketEvent and useSocketEmit hook thankfully to a module augmentation feature.

Create a file in your project called types/use-socket-io-react.d.ts and paste this.

import 'use-socket-io-react';

declare module 'use-socket-io-react' {
  interface ServerToClientEvents {
    chat: (message: string, sentAt: number) => void;
  }

  interface ClientToServerEvents {
    alert: (content: string) => void;
  }
}

These interfaces are copied directly from a backend. There is no need to worry about the specific conventions for this package. If on a backend server a TypeScript is used then it's easy to extend it.

const { emit } = useSocketEmit();

// Argument of type '[]' is not assignable to parameter of type '[content: string]'.
// Source has 0 element(s) but target requires 1.
emit('alert', []);

const handleMessage: EventHandler<'chat'> = ([message]) => {
  console.log(`There is a message ${message}`);
};

useSocketEvent('chat', {
  handler: handleMessage,
});

Additional notes

• Package uses the 4th major version of a socket.io-client.
• This project uses conventional commits convention
• This is still in development. But there are more incoming updates in the future!