How can I use a web worker to keep my UI responsive while processing large data in JavaScript?

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

        worker.onmessage = function(e) {
            console.log('Processed data:', e.data);
        };

        const largeData = [/* large data array */];
        worker.postMessage(largeData);

        // worker.js
        onmessage = function(e) {
            const data = e.data;
            // Simulate data processing
            const processedData = data.map(item => item * 2);
            postMessage(processedData);
        };
        <!-- END COPY / PASTE -->