[ITEM 2] QUESTION: What are Web Workers?

JavaScript is a single-threaded programming language, which means all code executes in a single main thread. If you perform complex mathematical calculations or process large amounts of data, the application interface will freeze and stop responding to user actions. To solve this problem, Web Workers were created, allowing JavaScript code to run in a separate background thread.

The main feature of this technology is isolation. Worker threads execute in parallel with the main user interface thread, but they have absolutely no access to the DOM tree, the window object, or the document object. Attempting to access page elements from a worker will result in an error.

Creating a background script is very simple. You instantiate an object using the new Worker('worker.js') construct, where you pass the path to the script file that will run in the background. After that, asynchronous data exchange is established between the main thread and the worker.

The postMessage method is used to send messages from the main thread to the worker. Inside the worker.js file itself, data is received via the global onmessage event. Feedback works in the exact same way: the worker can send the result of its work back to the main thread using its own postMessage, and the main thread will intercept it via the onmessage handler on the worker object.

Web Workers are ideal for resource-intensive tasks such as filtering large arrays of data, image processing, encryption, or file compression. Offloading heavy computations to background threads guarantees that the user interface remains smooth and responsive under any loads.