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useEffectOnce: Run an Effect Only Once

By FrontendAtlas Team · Updated Jan 30, 2026

This hook should run the effect only on mount and clean up on unmount, even under React StrictMode development behavior. Concepts: react, hooks, effects, lifecycle, components. Mention StrictMode double-invocation, cleanup idempotency, and tests for unexpected reruns or stale closures.

  • Implement useEffectOnce(effect) in useEffectOnce.ts.
  • The effect callback must run only once for the lifetime of a…

Challenge preview

useEffectOnce: Run an Effect Only Once: This hook should run the effect only on mount and clean up on unmount, even under React StrictMode development behavior. Concepts: react, hooks, effects,…. Expect react and hooks decisions under intermediate level constraints.

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