Concurrent Rendering Concepts
Modern React can prepare rendering work without immediately committing it. This enables prioritization and interruption so urgent interactions can remain responsive while less urgent work is prepared.
Concurrency does not mean JavaScript executes two component functions simultaneously on one thread. It means React can work on rendering in a way that is interruptible and schedulable.
This model makes render purity especially important. If rendering performs side effects, React's ability to pause, restart, or abandon work becomes unsafe.
Key distinction
Concurrent rendering is about scheduling and interruptibility of React work, not parallel execution of JavaScript component functions.
Key Takeaways
- Concurrent rendering requires pure render logic.
- React can prioritize urgent versus non-urgent updates.
- Never rely on a render occurring exactly once.