es module worker

fib.js

export function fibonacci(num) {
    if (num <= 1) return num;
    return fibonacci(num - 1) + fibonacci(num - 2);
  }

fibworker.js

import {Worker, isMainThread, parentPort, workerData} from 'worker_threads';
import { fibonacci as fib } from './fib.js';

console.log('script running');


export function calculateFibonacci(n) {
    console.log('isMain', isMainThread);
    if (isMainThread) {
        return new Promise((resolve, reject) => {
            console.log('starting worker');
            const worker = new Worker(new URL(import.meta.url).pathname, {
                workerData: n,
            });
            worker.on('message', (value) => {
                console.log('worker returned', value);
                resolve(value);
            });
            worker.on('error', reject);
            worker.on('exit', (code) => {
                console.log(`worker exit, code=${code}`)
                if (code !== 0) {
                    reject(new Error(`Worker stopped with exit code ${code}`));
                }
            });
        });
    } else {
        
    }
}

if (!isMainThread) {
    console.log('worker inited!');
    const result = fib(workerData);
    console.log('worker got result', result);
    parentPort.postMessage(result);
    console.log('worker posted result', result);
    process.exit(0);
}

index.js

import  express from 'express';
import {calculateFibonacci} from './fibworker.js';

const app = express()
const port = 3000

app.get('/fib', async (req, res) => {
  console.log('receiving req, start calc');
  const fibValue = await calculateFibonacci(42);
  res.send(`fib: ${fibValue}\n`)
})

app.get('/', (req, res) => {
  console.log('processing hello world start');
  res.send(`Hello World!\n`)
  console.log('processing hello world end');
})


app.listen(port, () => {
  console.log(`Example app listening on port ${port}`)
})

package.json

{
  "main": "index.js",
  "type": "module",
  "scripts": {
    "start": "nodemon index.js"
  },
  "dependencies": {
    "express": "^4.18.1"
  },
  "devDependencies": {
    "nodemon": "^2.0.19"
  }
}