Offload CPU-intensive tasks to worker threads in node.js, web browsers and electron using one uniform API.

Uses web workers in the browser, worker_threads in node 12+ and tiny-worker in node 8 to 11.

• First-class support for async functions & observables
• Write code once, run it on all platforms
• Manage bulk task executions with thread pools
• Use require() and import/export in workers
• Works great with webpack

You can find the old version 0.12 of threads.js on the v0 branch. All the content on this page refers to version 1.0 which is a rewrite of the library with a whole new API.

npm install threads tiny-worker

You only need to install the tiny-worker package to support node.js < 12. It's an optional dependency and used as a fallback if worker_threads are not available.

  npm install -D threads-plugin

+ const ThreadsPlugin = require('threads-plugin');

  module.exports = {
    // ...
    plugins: [
+     new ThreadsPlugin()
    ]
    // ...
  }

  module.exports = {
    // ...
+   externals: {
+     "tiny-worker": "tiny-worker"
+   }
    // ...
}

  module.exports = {
    // ...
    module: {
      rules: [
        {
          test: /\.ts$/,
          loader: "ts-loader",
+         options: {
+           compilerOptions: {
+             module: "esnext"
+           }
+         }
        }
      ]
    },
    // ...
  }

  import { spawn } from "threads"
+ import "threads/register"

  // ...

  const work = await spawn(new Worker("./worker"))

// master.js
import { spawn, Thread, Worker } from "threads"

const auth = await spawn(new Worker("./workers/auth"))
const hashed = await auth.hashPassword("Super secret password", "1234")

console.log("Hashed password:", hashed)

await Thread.terminate(auth)

// workers/auth.js
import sha256 from "js-sha256"
import { expose } from "threads/worker"

expose({
  hashPassword(password, salt) {
    return sha256(password + salt)
  }
})

The hashPassword() function of the auth object in the master code proxies the call to the hashPassword() function in the worker:

If the worker's function returns a promise or an observable then you can just use the return value as such in the master code. If the function returns a primitive value, expect the master function to return a promise resolving to that value.

Use expose() to make a function or an object containing methods callable from the master thread.

In case of exposing an object, spawn() will asynchronously return an object exposing all the object's functions. If you expose() a function, spawn will also return a callable function, not an object.

Find the full documentation on the website:

• Quick start
• Basic usage
• Using observables
• Thread pools
• Advanced

Threads.js works with webpack. Usually all you need to do is adding the threads-plugin.

See Build with webpack on the website for details.

We are using the debug package to provide opt-in debug logging. All the package's debug messages have a scope starting with threads:, with different sub-scopes:

• threads:master:messages
• threads:master:spawn
• threads:master:thread-utils
• threads:pool:${poolName || poolID}

Set it to DEBUG=threads:* to enable all the library's debug logging. To run its tests with full debug logging, for instance:

DEBUG=threads:* npm test

MIT