Rules and Best Practices for Hooks

🧠 What Are React Hooks?

React Hooks are special functions that let you “hook into” React features like state, context, lifecycle, and refs — all without writing class components. Hooks make your code simpler, reusable, and easier to manage. But to get the most out of them, you need to follow a few critical rules and best practices. ✅

⚠️ The 2 Golden Rules of Hooks

📍 1. Only Call Hooks at the Top Level

Hooks should always be called at the top of a component or another hook — never inside loops, conditions, or nested functions.

// ✅ Correct
function MyComponent() {
  const [count, setCount] = useState(0);
}

// ❌ Incorrect
if (condition) {
  const [count, setCount] = useState(0); // 🚫 Never do this!
}

Why? React relies on the order in which hooks are called to preserve state across renders. Breaking this rule will cause unpredictable bugs. 🐛

🔗 2. Only Call Hooks from React Functions

You should only use hooks:

• 🧠 Inside React function components
• 🛠️ Inside custom hooks

// ✅ Good
function useCustomHook() {
  const [value, setValue] = useState(0);
}

// ❌ Bad
function regularFunction() {
  const [value, setValue] = useState(0); // 🚫 Invalid
}

🧰 Best Practices for Using Hooks

📦 Keep Your Hooks Small and Focused

A hook should do one thing well. If it handles form logic, don’t mix it with API calls or modal toggles. Separation of concerns makes hooks easier to test, debug, and reuse. 🧼

🧩 Use Custom Hooks to Reuse Logic

If you find yourself duplicating logic across components (like input handling, timers, toggles), wrap that logic in a custom hook.

function useToggle(initial = false) {
  const [state, setState] = useState(initial);
  const toggle = () => setState(prev => !prev);
  return [state, toggle];
}

🔍 Always Provide Dependency Arrays

When using useEffect, useCallback, or useMemo, always include a proper dependency array to avoid stale data or unnecessary re-renders.

// ✅ Good
useEffect(() => {
  console.log('Data updated!');
}, [data]);

// ❌ Bad
useEffect(() => {
  console.log('Data updated!');
}); // Runs on every render 😬

🧠 Memoize Expensive Functions

Use useMemo or useCallback to optimize performance when passing heavy functions or derived values to child components.

const expensiveValue = useMemo(() => computeValue(input), [input]);
const memoizedCallback = useCallback(() => handleClick(id), [id]);

🪄 Keep useEffect Clean

Avoid cramming too much logic inside useEffect. Instead, extract functions and manage async calls responsibly:

// ✅ Clean and readable
useEffect(() => {
  async function fetchData() {
    const res = await fetch(url);
    setData(await res.json());
  }
  fetchData();
}, [url]);

📛 Name Custom Hooks with "use"

Custom hooks must start with the word use so React knows how to track their internal state. This is a convention and a rule.

// ✅ Correct
function useForm() { ... }

// ❌ Incorrect
function formHandler() { ... }

🔍 Debug with React DevTools

Use the React DevTools extension to inspect hook values in components. It helps debug state, effect runs, and performance issues. 🧪

🚫 Avoid Common Anti-Patterns

• ❌ Using hooks inside callbacks or event handlers
• ❌ Triggering re-renders by mutating useRef.current in render
• ❌ Passing unstable functions to useEffect without memoization

✅ Summary Checklist

• ✔️ Call hooks only at the top level
• ✔️ Use hooks only in React components or custom hooks
• ✔️ Separate hook logic into small, focused functions
• ✔️ Memoize expensive values or functions when needed
• ✔️ Always use dependency arrays
• ✔️ Use custom hooks to avoid duplication

🚀 Final Thoughts

Hooks revolutionized the way we write React code — but with great power comes great responsibility. By following these rules and best practices, you’ll write more robust, maintainable, and performant components that scale with confidence. 💪⚛️