React Hook Rules You Should Never Break
React Hook Rules You Should Never Break
React Hooks are a powerful feature that let you use state and other React features in functional components. However, to work correctly, hooks have some strict rules. Breaking these rules can cause bugs, unpredictable behavior, or errors.
1. Only Call Hooks at the Top Level
Do not call hooks inside loops, conditions, or nested functions.
Always call hooks at the top level of your React function component or custom hook.
This ensures hooks are called in the same order every time a component renders.
Why?
React relies on the order of hook calls to associate hook state correctly. Calling hooks conditionally can break this order.
Wrong:
jsx
Copy
Edit
if (userLoggedIn) {
useEffect(() => { /* ... */ });
}
Right:
jsx
Copy
Edit
useEffect(() => {
if (userLoggedIn) {
// your effect code
}
}, [userLoggedIn]);
2. Only Call Hooks from React Functions
Call hooks only from:
React function components
Custom hooks (functions whose names start with use)
Do not call hooks from regular JavaScript functions, class components, or outside React code.
3. Always Use Hooks in the Same Order
Hooks must be called in the same order on every render.
Changing the order breaks React’s internal hook state tracking.
4. Name Custom Hooks Starting with use
This naming convention lets React and other developers know the function uses hooks.
It also enables lint rules to enforce correct hook usage.
5. Avoid Side Effects Inside the Body of the Component
Hooks like useEffect are designed to handle side effects.
Do not perform side effects (like fetching data, subscriptions) directly inside the component function body.
Bonus: Use the ESLint Plugin for Hooks
Use the official eslint-plugin-react-hooks plugin.
It automatically warns you about violations of hook rules.
It helps catch mistakes early.
Summary
Rule Why?
Only call hooks at the top level Ensure consistent hook call order
Only call hooks from React functions Hooks rely on React’s internal logic
Call hooks in the same order every render Keep hook state stable
Name custom hooks with use prefix Enforce hook rules and clarity
Use useEffect for side effects Avoid side effects during render
Following these rules is essential for writing bug-free and maintainable React components using hooks. Breaking them will often lead to runtime errors or subtle bugs that are hard to debug.
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