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JourneyUncommon

React Patterns & Performance

Memo, refs, suspense, server components: production React.

Questions
15
Tier
Advanced
Language
React
Time
~20 min

Difficulty mix: 2 easy, 7 medium and 6 hard. The questions are drawn from the React library at the moment you start, so sitting the test twice does not give you the same paper.

What this test can pull from

42 React topics are in scope. These are the real topic labels on the questions.

  • useEffect dependency arrays
  • function components
  • what JSX is
  • embedding expressions
  • reconciliation diffing
  • custom hooks
  • lazy and Suspense
  • context and useContext
  • concurrent rendering tearing
  • forwardRef
  • useReducer
  • controlled vs uncontrolled
  • Server Components use client
  • fiber and lane priorities
  • render vs commit phase
  • React Router v6
  • hydration mismatches
  • React.memo bailout
  • bundler internals webpack vite
  • Server Actions
  • props read-only
  • useMemo
  • useCallback
  • useEffect vs useLayoutEffect timing
  • derived vs stored state
  • StrictMode double-invoke
  • automatic batching
  • stale-closure pitfalls
  • lifting state up
  • useSyncExternalStore

Questions of the kind this test asks

Six real React questions from the same pool, snippet included. The answer options and explanations are not shown here. Those come after you attempt them.

Prefer to pick your own questions? Browse all React questions. See the other 10 tests.