var worker = new Worker('worker.js');
worker.addEventListener('message', function(event) {
    console.log('message received from worker => ', event.data);
}); // listen to error event of worker
worker.addEventListener('error', function(event) {
    console.error('error received from worker => ', event);
});
worker.postMessage(null);
// worker.terminate(); // When worker needs to be terminated from main thread