HTML5 Web Workers in NodeJS? - html

Question

Anyone knows what the status of Web Worker support in NodeJS is? I found a two year old implementation, node-webworkers, but it didn't run with the current build of NodeJS.

Answer 1

Now there is https://github.com/audreyt/node-webworker-threads which appears to be actively maintained.

Answer 2

Worker Threads reached stable status in 12 LTS. Usage example
const {
Worker, isMainThread, parentPort, workerData
} = require('worker_threads');
if (isMainThread) {
module.exports = function parseJSAsync(script) {
return new Promise((resolve, reject) => {
const worker = new Worker(__filename, {
workerData: script
});
worker.on('message', resolve);
worker.on('error', reject);
worker.on('exit', (code) => {
if (code !== 0)
reject(new Error(`Worker stopped with exit code ${code}`));
});
});
};
} else {
const { parse } = require('some-js-parsing-library');
const script = workerData;
parentPort.postMessage(parse(script));
}

Answer 3

You can use the child processes, they solve similar problems.

Answer 4

You can look at the specifics of the HTML5 WebWorker source.
With a little care, you can 'redress' the WebWorker to fit as a Node.js worker, by adding a prelude that may look something like this:
const { parentPort } = require('worker_threads')
global.postMessage = function(msg){
parentPort.postMessage(msg)
}
var handler
global.addEventListener = function(kind, callback){
handler = callback
}
parentPort.on('message', msg => {
handler(msg)
})
The specific HTML5 worker added a message event handler using addEventListener, so I registered such a function in global and saved the handler. I also had to supply a postMessage implementation. Finally I registered a Node.js message handler that invokes the HTML5 handler.
Everything works perfectly. No need for any special dependency, just looking at the HTML5 worker code and identify the points where it deals with messages.