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Phase 9 · Connecting Frontend & Backend

Topics

Optimistic UI

Part of the Full Stack Developer Roadmap.

Summary

Updating the UI immediately as if a backend action succeeded, before the server actually confirms it, then rolling back if it fails — makes a full-stack app feel instant.

How to Learn This

  • 1Build a 'like' or toggle feature that updates instantly, then reverts on API failure.
  • 2Learn `useMutation`'s `onMutate`/`onError` in React Query for this pattern.
  • 3Consider the UX trade-off: speed vs occasionally showing a brief rollback.

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Loading & Error States

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Full-Stack Data Flow

More topics in Connecting Frontend & Backend

CORSAPI Integration with Fetch/AxiosReact Query / TanStack QueryEnvironment Variables & API URLsLoading & Error StatesFull-Stack Data FlowFile Uploads End-to-End
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