How does React handle state updates under the hood?

React schedules state updates using Fiber, queues them, and processes them based on priority before committing changes to the DOM.

When setState or a state setter from useState is called, React doesn't immediately update the DOM. Instead, it creates an update object and adds it to an internal queue. The Fiber reconciler then processes these updates based on priority lanes. High-priority updates (like user input) are processed first, while low-priority ones (like background rendering) can be delayed. React then performs reconciliation to compute the minimal set of DOM changes and finally commits them in the commit phase.