The answer
They run JavaScript on a separate thread. Heavy computation can be sent to a worker, and the main thread stays responsive (UI does not freeze). The worker posts results back via messages. This is the best way to handle CPU-intensive work.
Performance Tips for V8 JavaScript
How do Web Workers help with JavaScript performance?
More FAQs in Performance Tips for V8 JavaScript
Keep object shapes stable (same hidden class), keep functions monomorphic (same argument types), use dense arrays, avoid delete/eval/with, use const/let, break long tasks into chunks, use requestAnimationFrame for animations, debounce/throttle rapid events, and use Web Workers for heavy computation.
V8 assigns hidden classes based on object shape (property names and order). Objects with the same hidden class share optimized code. Different shapes cause deoptimization, which falls back to slower bytecode.
delete changes the object's hidden class, triggering a deoptimization. Instead of deleting a property, set it to null or undefined. This preserves the hidden class and keeps the optimized code path.
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