Lakhveer Singh Rajput

The Core Principles Every ReactJS Developer MUST Know

⚛️ The Core Principles Every ReactJS Developer MUST Know (With Hacks & Common Mistakes) 🚀

Write Less. Think Better. Build Faster.

React isn’t just a library—it’s a way of thinking. Many developers use React, but only a few truly understand it. If you want to level up from React user ➜ React engineer, this guide is for you 💡

🧠 1. Think in Components, Not Pages

“Divide and conquer” is React’s superpower.

✅ Principle

React apps are built using small, reusable, independent components.

❌ Mistake

Creating huge components doing too many things.

🔥 Hack

Follow SRP (Single Responsibility Principle):

• One component = One job

// ❌ Bad
function Dashboard() {
  // auth, data fetch, UI, logic — all together 😵
}

// ✅ Good
<Header />
<UserStats />
<ActivityList />

🔄 2. Unidirectional Data Flow (One-Way Binding)

Data flows top ➜ down, never the other way.

✅ Principle

Props are read-only. Child components cannot modify parent state.

❌ Mistake

Trying to update props directly.

// ❌ Wrong
props.count = props.count + 1;

🔥 Hack

Lift state up when multiple components need it.

const [count, setCount] = useState(0);

🎭 3. State vs Props – Know the Difference

❌ Mistake

Storing everything in state.

🔥 Hack

Ask yourself:

“Can this be derived from props?”

If yes ➜ Don’t use state

🧩 4. Declarative > Imperative

Tell React what you want, not how to do it.

❌ Imperative Thinking

document.getElementById("btn").style.display = "none";

✅ Declarative React

{isVisible && <Button />}

🔥 Hack

Your UI should be a pure function of state 🧮

🧠 5. Virtual DOM & Reconciliation

React doesn’t update the real DOM directly.

✅ Principle

• Creates a Virtual DOM
• Diffs changes
• Updates only what changed ⚡

❌ Mistake

Optimizing prematurely.

🔥 Hack

Use:

• React.memo
• useCallback
• useMemo

Only when performance issues appear

🔁 6. Keys Are NOT Optional

Keys help React identify what changed.

❌ Mistake

Using index as key.

items.map((item, index) => <Item key={index} />)

✅ Correct

items.map(item => <Item key={item.id} />)

🔥 Hack

Stable keys = fewer bugs + better performance

🎯 7. Side Effects Belong in useEffect

❌ Mistake

Fetching data directly inside render.

✅ Correct

useEffect(() => {
  fetchData();
}, []);

🔥 Hack

Think of useEffect as:

“React lifecycle in functional disguise” 😄

🧱 8. Composition Over Inheritance

React favors composition, not class inheritance.

❌ Mistake

Deep component inheritance chains.

✅ Better Pattern

<Card>
  <UserProfile />
</Card>

🔥 Hack

Use children to build flexible UI.

🔍 9. Controlled Components Win

❌ Uncontrolled

Letting DOM handle form state.

✅ Controlled

<input value={name} onChange={e => setName(e.target.value)} />

🔥 Hack

Controlled inputs = validation + consistency

⚡ 10. Don’t Overuse State Management Libraries

❌ Mistake

Using Redux for everything.

✅ Principle

Start with:

• useState
• useContext
• useReducer

🔥 Hack

“If React can handle it, let React handle it.”

🛠️ React Developer Power Hacks 💎

🚀 Use Custom Hooks

function useAuth() {
  const [user, setUser] = useState(null);
  return { user, login, logout };
}

🚀 Lazy Load Components

const Dashboard = React.lazy(() => import("./Dashboard"));

🚀 Error Boundaries

Prevent full app crashes 🛡️

🚨 Most Common React Mistakes to Avoid

❌ Mutating state directly ❌ Too many useEffects ❌ Missing dependency arrays ❌ Inline functions in heavy components ❌ Ignoring performance until production

🧘 Final Thought

React rewards clarity of thought. If you master its principles, React becomes predictable, scalable, and joyful ❤️

Build small, think declaratively, and let state drive UI.

📢 If you found this useful:

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Happy Coding! ⚛️🚀