Re-renders vs Commits: When to Optimize
Differentiate re-renders and commits; learn what triggers updates and when memoization is worth it.
Re-renders vs Commits: When to Optimize is a free React Academy lesson on CoddyKit — lesson 1 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.
Render vs commit
Goal: Know what a render is vs a commit.
- Render: compute next UI
- Commit: write changes to the DOM
- Bailouts: render may skip DOM work
Triggers for updates
Re-renders happen when state, props, or context used by a component change. Parent re-render ≠ child commit (if output is the same or memoized).
Demo: renders vs commits
Render count increases every time the component function runs; useEffect shows commits (after DOM is updated).
<div id="root"></div>
Demo: memoized child
React.memo skips re-render if props are shallow-equal. Toggling an unrelated parent state won’t re-render the memoized child.
<div id="root"></div>
When to optimize
Optimize when:
- Profiling shows slow renders
- Large lists or heavy children
- Stable props/handlers enable memoization
Otherwise keep code simple first.
Pitfalls & notes
Avoid:
- Memoizing everything (adds complexity)
- Changing prop identities each render
- Confusing parent re-render with child DOM updates
Render vs commit check
Recap
Recap: Renders compute UI; commits touch the DOM. Optimize when profiling says so, and use React.memo when props stay stable.
Frequently asked questions
Is the “Re-renders vs Commits: When to Optimize” lesson free?
Yes — the full text of “Re-renders vs Commits: When to Optimize” 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 “Re-renders vs Commits: When to Optimize”?
Differentiate re-renders and commits; learn what triggers updates and when memoization is worth it. 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 1 of 3, so you can start here or from the beginning and move at your own pace.
How long does the “Re-renders vs Commits: When to Optimize” 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