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React Academy · Lesson

Persisting Values Without Re-render

Keep mutable values across renders without triggering re-render; compare useRef vs useState with simple counters and a timer id.

Persisting Values Without Re-render 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.

Why useRef?

Aim: Store values that survive re-renders without causing a new render. useRef gives you a stable .current box.

  • Persists across renders
  • No re-render on change
  • Great for timers, previous values

Ref vs State

useState updates re-render the UI. useRef updates do not. Pick ref for mutable helpers (ids, counters for logic), not for UI data.

Demo: render counter with ref

We increment a renderCount in an effect and keep it in a ref; it survives renders but doesn't trigger them.


<div id="root"></div>

Good fits for useRef

Good fits:

  • Timer/interval ids
  • Previous value caches
  • Flags between renders (e.g., isMounted)

Not for: data that must appear in the UI.

Demo: timer id in ref

Keep the interval id in a ref so we can start/stop the timer without extra renders.


<div id="root"></div>

Pitfalls & tips

Pitfalls:

  • Do not read a ref to drive UI without state—UI won't update.
  • Reset refs on unmount if they hold ids/resources.
  • Avoid overusing refs as global bags.

useRef concept check

Which hook lets you persist a mutable value across renders without causing a re-render when it changes?

Recap

Recap: Use useRef for mutable values that live across renders—like ids, previous values, or flags—without causing re-renders. Use state for visible UI.

Frequently asked questions

Is the “Persisting Values Without Re-render” lesson free?

Yes — the full text of “Persisting Values Without Re-render” 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 “Persisting Values Without Re-render”?

Keep mutable values across renders without triggering re-render; compare useRef vs useState with simple counters and a timer id. 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 “Persisting Values Without Re-render” 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

  1. Persisting Values Without Re-render
  2. Accessing DOM Nodes, Measuring & Focusing
  3. Mutable Refs for Timers & IDs
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