React.memo, useMemo, useCallback — In Practice
Use React.memo to skip child re-renders, useMemo for derived values, and useCallback for stable handler identities.
React.memo, useMemo, useCallback — In Practice is a free React Academy lesson on CoddyKit — lesson 2 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What each tool does
Goal: Use three tools:
- React.memo — skip child re-render if props are equal
- useMemo — memoize derived values
- useCallback — stable function props
When it helps
Use when:
- Child is expensive or often unchanged
- Derived data is heavy or stable
- Handlers are passed to memoized children
Profile before over-optimizing.
Memo child and handlers
React.memo skips re-render if props are the same. Pair with useCallback to keep handler identity stable.
<div id="root"></div>
Derived values with useMemo
Compute a derived list with useMemo so its identity stays stable unless inputs change.
<div id="root"></div>
Stable handlers with useCallback
Pass a stable onSelect to a memoized row so unchanged rows don't re-render.
<div id="root"></div>
Tips & pitfalls
Tips:
- Memoize only where it pays off
- Keep dependency arrays correct
- Prefer stable props to help React.memo
Memo + stable handlers check
Recap
Recap: React.memo skips re-renders on equal props, useMemo stabilizes derived values, and useCallback keeps handler identities stable.
Frequently asked questions
Is the “React.memo, useMemo, useCallback — In Practice” lesson free?
Yes — the full text of “React.memo, useMemo, useCallback — In Practice” is free to read here on the web, and the React Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Academy course, upgrade to CoddyKit PRO.
What will I learn in “React.memo, useMemo, useCallback — In Practice”?
Use React.memo to skip child re-renders, useMemo for derived values, and useCallback for stable handler identities. You practise React Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start React Academy?
No prior experience is required. React Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “React.memo, useMemo, useCallback — In Practice” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this React Academy lesson?
Yes. Every React Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Re-renders vs Commits: When to Optimize
- React.memo, useMemo, useCallback — In Practice
- Derived State & Avoiding Extra Renders