worker and main thread communicate by postMessage and addEventListener

main.js

const worker = new Worker('worker.js')

// handle data from worker
worker.addEventListener('message', (e) => {
  console.log('worker send data back:', e.data)
}, false);

// handle error
worker.addEventListener('error', (err) => {
  console.log(`Error: Line ${err.lineno} in ${err.filename} : ${e.message}`);
}, false)

worker.postMessage('hello'); // send data to worker, large data typically

worker.js

function handleData(data) {
  // handle data and return
}

self.addEventListener('message', (e) => {
  // handle data from e.data and send data to main thread
  const result = handleData(e.data);
  self.postMessage(result); 
}, false);

stop worker has two ways:

1. worker.terminate() in main thread:

const worker = new Worker('worker.js')
worker.terminate();

2. self.close() in worker:

self.close();