How to handle Child Threads in Node.js ?

// Do any work in parallel to main
// event loop or main process
console.log('Child Process Starts')
setTimeout(() => {
    console.log('Data processed')
}, 5000)

const { fork } = require('child_process');
 
// Fork another process
const child_process = fork('./parallelProcess.js');

// Data we may need to send to the child process
const data = {} 

console.log('Before process')

// Send the data to forked process
child_process.send({ data }, function(){
    console.log('Sending data')
});

// Listen to forked process 
child_process.on('close', (result) => {
    console.log('Child process terminated and returned');
});

console.log('After process')

const {Worker, isMainThread, parentPort} 
            = require('worker_threads');

if (isMainThread) {

    // Main code, only executed for main thread
    const worker = new Worker(__filename, {
        workerData: {}
    });

    worker.on('message', (m) => console.log(
                  'Thread send message:', m));

    worker.on('error', () => console.log('Error'));
    worker.on('exit', () => {
        console.log('Worker exit')
    });
} else {

    // Worker thread code, only execute
    // for working thread.
    setTimeout(() => {
        parentPort.postMessage('Hello World!');
    }, 3000)
}