<!-- BEGIN COPY / PASTE -->
        // Main thread
        const worker = new Worker('worker.js');
        worker.postMessage('Hello from main thread');

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

        // worker.js
        self.onmessage = function(event) {
            console.log('Received from main thread:', event.data);
            self.postMessage('Hello from worker');
        };
        <!-- END COPY / PASTE -->