postMessage로 메시지 주고받기

const worker = new Worker('worker.js');
worker.postMessage({ task: 'sum', numbers: [1, 2, 3, 4] });

// worker.js
self.onmessage = (event) => {
  const { task, numbers } = event.data;
  console.log('worker received task:', task);
};

// worker.js
self.onmessage = (event) => {
  const { numbers } = event.data;
  const total = numbers.reduce((a, b) => a + b, 0);
  self.postMessage(total); // send result back
};

worker.onmessage = (event) => {
  console.log('result from worker:', event.data);
};

worker.addEventListener('message', (event) => {
  console.log('got:', event.data);
});

// OK to send: numbers, strings, plain objects, arrays,
// Map, Set, Date, ArrayBuffer, typed arrays.
// NOT cloneable: functions, DOM nodes, Error stacks lost.

// main:
worker.postMessage({ type: 'multiply', a: 6, b: 7 });

// worker.js:
self.onmessage = (e) => {
  if (e.data.type === 'multiply') {
    self.postMessage(e.data.a * e.data.b);
  }
};

// main: worker.postMessage({ id: 42, value: 'x' });
// worker: self.postMessage({ id: e.data.id, done: true });
// main can now match reply id 42 to its request.

// Worker can report progress repeatedly:
// self.postMessage({ type: 'progress', percent: 50 });
// self.postMessage({ type: 'done', result: data });

worker.onmessage = null;
worker.terminate();