fibonacci.js

import {Worker, Agent} from '@mapbox/workerpool';

// only used on the worker side
export class FibonacciWorker extends Worker {
    calculate(num, callback) {
        let a = 1;
        let b = 0;
        for (let i = num; num >= 0; num--) {
            const tmp = a;
            a += b;
            b = tmp;
        }
        callback(null, b);
    }
}

// only used on the main thread
export class FibonacciAgent extends Agent {
    calculate(num, callback) {
        this.send('calculate', num, callback);
    }
};

main.js

// main thread entry point

import {WorkerPool, registerAgent} from '@mapbox/workerpool';
import {FibonacciAgent} from './fibonacci.js';

WorkerPool.create(4, './worker_bundle.js');

registerAgent(FibonacciAgent, 'Fibonacci');

for (let i = 0; i < 8; i++) {
    const fibonacci = new FibonacciAgent();
    fibonacci.calculate(i, (err, result) => console.log(result));
}

worker.js

// worker entry point

import {registerWorker} from '@mapbox/workerpool';
import {FibonacciWorker} from './fibonacci.js';

registerWorker(FibonacciWorker, 'Fibonacci');