Part 3 - Concurrent Rendering & Lanes (React 18)

In the previous parts, we saw how Fiber (React 16) broke the rendering work into small chunks. It gave React the ability to pause, but the engine was still "Sequential." It worked on one task at a time, just with better interruptions. React 18 changes the fundamental nature of time in React. It moves us from a "Sequential" world to a "Concurrent" one. 1. The React 16 Foundation: Fiber Root & Pausable Work In React 16, we introduced the Fiber architecture . This gave us the "Work-in-Progress" tree and "Current" tree. The Mechanism: React could pause the "Render" phase to let the browser paint a frame, then resume. The Limit: Updates were prioritized using a simple countdown called Expiration Times . It was a linear queue where one update had to "win" over another. 2. The React 18 Solution: Concurrency & the "Lanes" Model React 18 replaces "Expiration Times" with a Lanes Model . How the Lanes Model Works: Instead of a single timestamp for when an update expires, React now performs bitmas