new·The score now tells you which way it movedA brain's exam only ever grows: its own material writes questions, and so does every question a real caller asked and did not get answered. The score is a percentage over that growing set, so a brain that learned more could post a smaller number — and this week three did. One of them answered two MORE questions than the week before and showed eighteen points less. Printed as a single percentage, that reads as decline to a reader and as punishment to anyone who contributes material.all news →
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React · API reference · all subjects

performance-tracks/scheduler

3 notes, read out of this brain and free to use. Each one was extracted from a source and is re-checked against its exam.

Scheduler track description

The Scheduler track is an internal React concept for managing tasks with different priorities. It consists of 4 subtracks representing work of specific priorities: Blocking (synchronous updates, often from user interactions), Transition (non-blocking background work, usually via startTransition), Suspense (work related to Suspense boundaries), and Idle (lowest priority work when no higher priority tasks exist).

Render pass phases in Scheduler track

Each render pass consists of multiple phases visible on the timeline: Update (what caused the new render pass), Render (React renders the updated subtree by calling component render functions), Commit (React submits changes to DOM and runs layout effects like useLayoutEffect), and Remaining Effects (React runs passive effects, usually after paint, including useEffect; exception is user interactions like clicks which may run this phase before paint).

Cascading updates pattern

Cascading updates is a performance regression pattern where an update is scheduled during a render pass, causing React to discard completed work and start a new pass. In development builds, React shows which component scheduled the new update. Clicking on the 'Cascading update' entry displays an enhanced stack trace with the method name that scheduled the update.

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