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/components

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

Components track visualization

The Components track displays the durations of React components as a flamegraph, where each entry represents the duration of the corresponding component render and all its descendant children components. Effect durations are also represented as a flamegraph with a different color scheme aligned to the Scheduler track phases.

Components track effects display threshold

Not all effects are shown on the Components track by default. To maintain performance and prevent UI clutter, React only displays effects with a duration of 0.05ms or longer, or effects that triggered an update.

Components track lifecycle events

The Components track displays additional events during render and effects phases: Mount (a corresponding subtree of component renders or effects was mounted), Unmount (a corresponding subtree was unmounted), Reconnect (similar to Mount but only when <Activity> is used), and Disconnect (similar to Unmount but only when <Activity> is used).

Changed props inspection in Components track

In development builds, clicking on a component render entry in the Components track allows inspection of potential changes in props. This information can be used to identify unnecessary renders.

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