Easy communication with a Web Worker
or Service Worker from React.

React component for easy communication with a Web Worker. Leverages the Render Props pattern for ultimate flexibility as well as the new Context API for ease of use. Just specify the public url to your Web Worker and you'll get access to any messages or errors it sends, as well as the postMessage handler. Also works with Service Workers.

• Zero dependencies
• Choose between Render Props and Context-based helper components
• Provides timestamped messages and errors
• Provides easy access to the last message data and last error
• Provides postMessage to send messages to the Web Worker
• Provides updatedAt and lastPostAt metadata
• Accepts parser and serializer for automatic message (de)serialization
• Accepts onMessage and onError callbacks
• Supports custom Worker instance through the worker prop (new in v2)
• Supports communication with Service Workers (new in v2.1)

This package was modeled after React Async which helps you deal with Promises in React.

Install

npm install --save react-webworker

Usage

Using render props for ultimate flexibility:

import WebWorker from "react-webworker"

const MyComponent = () => (
  <WebWorker url="/worker.js">
    {({ data, error, postMessage }) => {
      if (error) return `Something went wrong: ${error.message}`
      if (data)
        return (
          <div>
            <strong>Received some data:</strong>
            <pre>{JSON.stringify(data, null, 2)}</pre>
          </div>
        )
      return <button onClick={() => postMessage("hello")}>Hello</button>
    }}
  </WebWorker>
)

Using helper components (don't have to be direct children) for ease of use:

import WebWorker from "react-webworker"

const MyComponent = () => (
  <WebWorker url="/worker.js">
    <WebWorker.Pending>
      {({ postMessage }) => <button onClick={() => postMessage("hello")}>Hello</button>}
    </WebWorker.Pending>
    <WebWorker.Data>
      {data => (
        <div>
          <strong>Received some data:</strong>
          <pre>{JSON.stringify(data, null, 2)}</pre>
        </div>
      )}
    </WebWorker.Data>
    <WebWorker.Error>{error => `Something went wrong: ${error.message}`}</WebWorker.Error>
  </WebWorker>
)

Usage with Parcel or worker-plugin for Webpack

Parcel and worker-plugin allow your Web Worker script to be automatically bundled. However this only works when you create the Worker instance yourself, instead of having react-webworker do it for you. Here's how that works:

import WebWorker from "react-webworker"

const myWorker = new Worker("./worker.js") // relative path to the source file, not the public URL

const MyComponent = () => <WebWorker worker={myWorker}>...</WebWorker>

The downside to this approach is that <WebWorker> will not manage the Worker's lifecycle. This means it will not automatically be terminated when <WebWorker> is unmounted.

Communicating with a Service Worker

Using <WebWorker> with a Service Worker is as simple as passing it as a custom worker instance:

const MyComponent = () => <WebWorker worker={navigator.serviceWorker}>...</WebWorker>

This will automatically setup a MessageChannel to enable bidirectional communication. Your Service Worker could look like this:

// `ports` is automatically provided with a MessageChannel port
self.onmessage = ({ data, ports: [port] }) => {
  console.log("inside the service worker:", data)
  port.postMessage(data) // instead of `self.postMessage`
}

Note that messages sent to an inactive (not "activated") Service Worker will be silently ignored. Like a custom Worker, you'll have to deal with the Service Worker lifecycle yourself.

API

Props

<WebWorker> takes the following properties:

• url {string} (required) Public url to the Web Worker file (or path relative to the root of your domain)
• options {Object} Options passed to the Worker constructor
• worker {Worker} An existing Worker instance to use instead of creating a new one (ignoring url and options)
• parser {Function} Transforms incoming message data (not errors)
• serializer {Function} Transforms postMessage payload before sending
• onMessage {Function} Callback function invoked when a message is received, passing message data as argument
• onError {Function} Callback function invoked when an error is received, passing error object as argument

url and options are evaluated at mount time, so they must be defined immediately and won't respond to changes.

A custom Worker provided through worker will not get terminated on unmount. You'll have to manage its lifecycle yourself.

Render props

<WebWorker> provides the following render props:

• messages {Array} list of received messages ({ data, date }), in chronological order
• errors {Array} list of received errors ({ error, date }), in chronological order
• data {any} last received message data, maintained when an error is received
• error {Error} last received error, cleared when new message arrives
• updatedAt {Date} when the last message or error was received
• postMessage {Function} sends a message to the Web Worker

Note: it's recommended to send and receive JSON strings instead of JS objects for improved performance. You can use the parser and serializer props to have <WebWorker> deal with this on the client side, but your Worker must still (de)serialize messages on its end.

Examples

Using lastPostAt to show a loading indicator

import WebWorker from "react-webworker"

const MyComponent = () => (
  <WebWorker url="/worker.js">
    {({ data, error, postMessage, updatedAt, lastPostAt }) => (
      <div>
        {data && (
          <div>
            <strong>Received some data:</strong>
            <pre>{JSON.stringify(data, null, 2)}</pre>
          </div>
        )}
        <button onClick={() => postMessage("hello")} disabled={updatedAt < lastPostAt}>
          {updatedAt < lastPostAt ? "Loading..." : "Go"}
        </button>
      </div>
    )}
  </WebWorker>
)

Passing options to the Worker

import WebWorker from "react-webworker"

const MyComponent = () => (
  <WebWorker url="/worker.js" options={{ type: "module", credentials: "include" }}>
    ...
  </WebWorker>
)

Using parser and serializer to automatically parse incoming messages and stringify outgoing messages

import WebWorker from "react-webworker"

const MyComponent = () => (
  <WebWorker url="/worker.js" parser={JSON.parse} serializer={JSON.stringify}>
    {({ data, error, postMessage, updatedAt, lastPostAt }) => (
      <div>
        {data && (
          <div>
            <strong>Received some data:</strong>
            <pre>{JSON.stringify(data, null, 2)}</pre>
          </div>
        )}
        <button onClick={() => postMessage({ foo: "bar" })}>Send</button>
      </div>
    )}
  </WebWorker>
)

Note: the Worker must still implement JSON (de)serialization on its own end.

Helper components

<WebWorker> provides several helper components that make your JSX even more declarative. They don't have to be direct children of <WebWorker> and you can use the same component several times.

<WebWorker.Data>

Renders only when a message has been received.

Props

• children {Function|Node} Render function which receives last message data and props object or just a plain React node.

Examples

<WebWorker.Data>{data => <pre>{JSON.stringify(data)}</pre>}</WebWorker.Data>

<WebWorker.Error>

Renders only when an error has been received.

Props

• children {Function|Node} Render function which receives error and props object or just a plain React node.

Examples

<WebWorker.Error>{error => `Unexpected error: ${error.message}`}</WebWorker.Error>

<WebWorker.Pending>

Renders only when no message or error has been received yet. Enable persist to ignore errors.

Props

• persist {boolean} Show until we receive message data, even when an error is received.
• children {Function|Node} Function which receives props object or React node.