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. This is 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, and your progress syncs across the web and the CoddyKit app. The React Academy course includes 3 lessons in total.
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. 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. The React Academy course includes 3 lessons in total.
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, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 3.
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