6 Secret React useEffect Techniques Used by Professional Teams (But Never on Pape


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useEffect is that hook you think you know about… until you work with a senior engineering team and discover they're handling it like a Swiss Army knife. I learned a few "obvious in hindsight" techniques over the years, which never get written down but make a huge difference in production React applications.


These are six secrets that distinguish weekend coders from professionals.


1. Separate Concerns With Multiple useEffect Calls

Most newbies pile all the things into a single useEffect. Professionals divide them by duty:


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// ❌ Bad — unrelated logic all grouped together

useEffect(() => {

  fetchData();

  window.addEventListener('resize', handleResize);

  return () => window.removeEventListener('resize', handleResize);

}, []);


// ✅ Good — separated into distinct effects

useEffect(fetchData, []);

useEffect(() => {

  window.addEventListener('resize', handleResize);

return () => window.removeEventListener('resize', handleResize);

}, []);


Why it matters: It makes cleanup code deterministic and easy to debug.


2. Use "Effect Guards" to Avoid Unnecessary Work

Occasionally you might not need your effect to execute on initial mount — only on updates.


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const isFirstRun = useRef(true);

useEffect(() => {

  if (isFirstRun.current) {

    isFirstRun.current = false;

    return;

  }

  doSomethingOnUpdate();

}, [someValue]);

Pro tip: This pattern avoids wasted API calls and costly computations.


3. Sync External State Without Race Conditions

If your effect touches state based on async calls, always keep a flag around whether the component is still mounted.


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useEffect(() => {

  let isActive = true;

  fetchData().then(data => {

    if (isActive) setData(data);

  });

  return () => { isActive = false; };

}, []);

Why it matters: Avoids React warnings and state leaks when rapidly navigating.


4. Memoize Inside the Effect for Stability

When your effect relies on a callback, memoize it using useCallback to prevent infinite loops.


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const stableHandler = useCallback(() => {

  // stable logic here

}, [dep]);


useEffect(() => {

  window.addEventListener('scroll', stableHandler);

  return () => window.removeEventListener('scroll', stableHandler);

}, [stableHandler]);

Without useCallback: The effect cleans up and re-attaches on every render. Yikes.


5. Batch State Updates to Prevent Re-Renders

Within async effects, you can batch state updates for better performance:


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import { unstable_batchedUpdates } from 'react-dom';


useEffect(() => {

  async function load() {

    const [user, settings] = await Promise.all([

      fetchUser(),

      fetchSettings()

    ]);

    unstable_batchedUpdates(() => {

      setUser(user);

setSettings(settings);

});

}

load();

}, []);Why it matters: Eliminates unnecessary re-renders, particularly with several state updates.


6. Avoid useEffect Altogether When You Can

Dirty secret: there are a lot of useEffects that are not needed.

Instead of responding to state changes, derive the data directly:


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// ❌ Overusing useEffect

useEffect(() => {

  setFullName(`${first} ${last}`);

}, [first, last]);


// ✅ Derived state without effect

const fullName = `${first} ${last}`;

Why it matters: Less code, less bugs, quicker renders.


Final Thoughts

useEffect is great, but overusing or abusing it silently destroys performance and complexity. Serious teams work with effects as side-effect handlers, not state machines. Separate them, protect them, stabilize them, and—where you can—eliminate them.


The greatest useEffect is usually the one you never wrote.


If you would like, I can also provide you with a brief "tweetable" summary of each tip so that you can share this blog post on social media. Would you like me to do that?