Sarah Thompson

Asked: February 20, 2025In: ReactJs

What is React.memo?

Added an answer on February 20, 2025 at 10:35 am

What is React.memo? React.memo is a Higher-Order Component (HOC) in React that memoizes functional components, preventing unnecessary re-renders when props haven't changed. 🧠 Think of it as: PureComponent but for functional components. 🔥 Performance Boost: Helps optimize re-renders for components thRead more

What is `React.memo`?

React.memo is a Higher-Order Component (HOC) in React that memoizes functional components, preventing unnecessary re-renders when props haven’t changed.

🧠 Think of it as: PureComponent but for functional components.
🔥 Performance Boost: Helps optimize re-renders for components that receive the same props frequently.

🛠️ Basic Syntax:

MyComponent will only re-render if its props change.

🧩 Example Without `React.memo` (Unnecessary Re-renders):

import React, { useState } from 'react';

const Child = ({ name }) => {
console.log('Child re-rendered'); // Logs on every parent render
return <h2>Hello, {name} 👋</h2>;
};

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

return (
<div>
<h1>Count: {count}</h1>
<button onClick={() => setCount(count + 1)}>Increment ➕</button>
<Child name="Naveen" />
</div>
);
};

export default Parent;

🛑 Issue:

Every time you click “Increment”, the Child re-renders—even though its name prop hasn’t changed.

✅ Optimized with `React.memo`:

import React, { useState } from 'react';

const Child = React.memo(({ name }) => {
console.log('Child re-rendered'); // Only logs when `name` changes
return <h2>Hello, {name} 👋</h2>;
});

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

return (
<div>
<h1>Count: {count}</h1>
<button onClick={() => setCount(count + 1)}>Increment ➕</button>
<Child name="Naveen" />
</div>
);
};

export default Parent;

🚀 What Changed?

React.memo wraps the Child component.
Now, Child only re-renders if the name prop changes.
Clicking the button increments the counter but doesn’t re-render Child.

⚡ When to Use `React.memo`?

✅ Components that render frequently with the same props.
✅ Components that are expensive to render (e.g., heavy UI logic).
✅ Pure components with simple props.

⚠️ When NOT to Use `React.memo`?

❌ For components with dynamic or complex props (e.g., functions or objects that change references).
❌ If the re-render cost is negligible—over-optimizing can backfire.

🧠 Advanced: Using `React.memo` with `areEqual` Function

To control re-renders more precisely, pass a custom comparison function.

const Child = React.memo(({ user }, prevProps) => {
return prevProps.user.id === user.id;
});

const Parent = () => {
const [user, setUser] = useState({ id: 1, name: 'Naveen' });

return <Child user={user} />;
};

Here, Child will only re-render if the user.id changes, ignoring changes in other properties.

🚀 Pro Tip:

Pair React.memo with useMemo or useCallback for props that are functions or objects to avoid reference changes.
Use it wisely! Overusing React.memo can lead to premature optimizations.

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Asked: February 20, 2025In: ReactJs

What is the difference between Redux and Context API?

Sarah Thompson Beginner

Added an answer on February 20, 2025 at 10:32 am

Redux vs. Context API in React Both Redux and React Context API help manage state in React apps, but they serve different purposes and scales. 📊 High-Level Comparison Feature Redux Context API Purpose Global state management with advanced features Prop drilling avoidance & simple global state StRead more

Redux vs. Context API in React

Both Redux and React Context API help manage state in React apps, but they serve different purposes and scales.

📊 High-Level Comparison

Feature	Redux	Context API
Purpose	Global state management with advanced features	Prop drilling avoidance & simple global state
State Management	Uses centralized store	Uses React’s built-in Context
Boilerplate	More setup (actions, reducers, store)	Minimal setup
Performance	Optimized for large-scale apps	Can cause unnecessary re-renders
DevTools Support	Powerful Redux DevTools	No built-in DevTools
Middleware	Supports (e.g., Redux Thunk, Redux Saga)	No native middleware
Best For	Large, complex applications	Small to medium apps with simple state needs

🛠️ Context API Example

Good for lightweight global state needs (e.g., theme toggling, user authentication)

import React, { createContext, useContext, useState } from 'react';

// 1️⃣ Create Context
const ThemeContext = createContext();

const App = () => {
const [darkMode, setDarkMode] = useState(false);

return (
// 2️⃣ Provide Context
<ThemeContext.Provider value={{ darkMode, setDarkMode }}>
<Header />
</ThemeContext.Provider>
);
};

const Header = () => <ThemeToggle />;

const ThemeToggle = () => {
// 3️⃣ Consume Context
const { darkMode, setDarkMode } = useContext(ThemeContext);

return (
<button onClick={() => setDarkMode(!darkMode)}>
{darkMode ? 'Switch to Light Mode 🌞' : 'Switch to Dark Mode 🌙'}
</button>
);
};

export default App;

⚡ Key Points:

Minimal setup.
Great for non-frequent updates.
Performance issues may arise if used for rapidly changing states (e.g., real-time data).

🛠️ Redux Example

Ideal for complex applications with multiple slices of state and advanced needs.

1️⃣ Install Redux Toolkit & React-Redux:

2️⃣ Create a Redux Store:

// store.js
import { configureStore, createSlice } from '@reduxjs/toolkit';

const counterSlice = createSlice({
name: 'counter',
initialState: { value: 0 },
reducers: {
increment: (state) => { state.value += 1; },
decrement: (state) => { state.value -= 1; },
},
});

export const { increment, decrement } = counterSlice.actions;

export const store = configureStore({
reducer: {
counter: counterSlice.reducer,
},
});

3️⃣ Connect Redux to React:

// App.js
import React from 'react';
import { Provider, useDispatch, useSelector } from 'react-redux';
import { store, increment, decrement } from './store';

const Counter = () => {
const count = useSelector((state) => state.counter.value);
const dispatch = useDispatch();

return (
<div>
<h1>Count: {count}</h1>
<button onClick={() => dispatch(increment())}>➕ Increment</button>
<button onClick={() => dispatch(decrement())}>➖ Decrement</button>
</div>
);
};

const App = () => (
<Provider store={store}>
<Counter />
</Provider>
);

export default App;

⚡ Key Points:

Centralized store holds app-wide state.
Reducers handle logic for state changes.
Optimized with Redux Toolkit for less boilerplate.

🚀 When to Use Context API?

✅ Small to medium apps.
✅ Non-frequently updated global state (e.g., theme, user info).
✅ Avoids prop drilling without extra dependencies.

🚀 When to Use Redux?

✅ Large, complex apps.
✅ Apps with frequent state updates or deeply nested components.
✅ When you need middleware, time-travel debugging, or complex state logic.

⚡ Pro Tip:

Redux Toolkit has streamlined Redux, making it almost as simple as Context API but with better performance for large-scale apps.
If your app is simple, go with Context API. If it’s complex or growing fast, go with Redux.

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Asked: February 20, 2025In: ReactJs

What is server-side rendering in React?

Sarah Thompson Beginner

Added an answer on February 20, 2025 at 10:28 am

Server-Side Rendering (SSR) is the process of rendering React components on the server and sending the fully rendered HTML to the client. This improves initial page load speed, SEO, and performance. 🆚 Client-Side Rendering vs. Server-Side Rendering Client-Side Rendering (CSR) Server-Side Rendering (Read more

Server-Side Rendering (SSR) is the process of rendering React components on the server and sending the fully rendered HTML to the client. This improves initial page load speed, SEO, and performance.

🆚 Client-Side Rendering vs. Server-Side Rendering

Client-Side Rendering (CSR)	Server-Side Rendering (SSR)
Renders components in the browser	Renders components on the server
Slower initial load (blank HTML)	Faster initial load (pre-rendered HTML)
Better for dynamic apps	Better for SEO and performance
Example: Create React App	Example: Next.js

🚀 SSR with Next.js (Popular SSR Framework for React)

Next.js makes SSR simple in React. It uses special functions like getServerSideProps for SSR.

1️⃣ Setting Up Next.js

2️⃣ Example: SSR in Next.js

// pages/index.js
export default function Home({ user }) {
return (
<div>
<h1>Welcome, {user.name}! 👋</h1>
<p>Email: {user.email}</p>
</div>
);
}

// This function runs on the server at request time
export async function getServerSideProps() {
// Simulating data fetching (e.g., API call)
const user = {
name: 'Naveen',
email: 'naveen@example.com',
};

// Pass data as props to the page component
return {
props: { user },
};
}

⚡ How It Works:

getServerSideProps runs on every request.
Fetches data on the server.
Sends pre-rendered HTML with user data to the client.
No loading spinners—the data is already there when the page loads.

3️⃣ API Call Example in SSR

export async function getServerSideProps() {
const res = await fetch('https://jsonplaceholder.typicode.com/users/1');
const user = await res.json();

return { props: { user } };
}

This fetches live data from an API on the server before sending the page.

🌟 Why Use SSR?

✅ SEO Benefits — Pre-rendered content is crawlable.
✅ Faster Initial Load — Especially for users on slow networks.
✅ Dynamic Data — Ensures fresh data on every request.

🚫 When Not to Use SSR?

❌ Static content — use Static Site Generation (SSG) instead.
❌ Highly interactive pages — CSR may be better.

⚡ Pro Tip:

Combine SSR with Client-Side Rendering for interactive parts.
Use Incremental Static Regeneration (ISR) in Next.js for hybrid solutions.

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Asked: February 20, 2025In: ReactJs

How do you handle events in React?

Sarah Thompson Beginner

Added an answer on February 20, 2025 at 10:24 am

⚡ Handling Events in ReactJS Event handling in React is similar to handling events in plain JavaScript, but with some tweaks: Use camelCase for event names (onClick instead of onclick). Pass a function directly, not a string (onClick={handleClick}). 1️⃣ Handling Click Events import React from 'reactRead more

⚡ Handling Events in ReactJS

Event handling in React is similar to handling events in plain JavaScript, but with some tweaks:

Use camelCase for event names (onClick instead of onclick).
Pass a function directly, not a string (onClick={handleClick}).

1️⃣ Handling Click Events

import React from 'react';

const ClickExample = () => {
const handleClick = () => {
alert('Button Clicked! 🚀');
};

return (
<button onClick={handleClick}>Click Me</button>
);
};

export default ClickExample;

🛠️ Explanation:

onClick triggers handleClick when the button is clicked.

2️⃣ Passing Arguments to Event Handlers

const ArgumentExample = () => {
const greetUser = (name) => {
alert(`Hello, ${name}! 🎉`);
};

return (
<button onClick={() => greetUser('Naveen')}>Greet</button>
);
};

export default ArgumentExample;

🛠️ Note:

Arrow function is used to pass arguments.
Without the arrow function, the function would execute immediately.

3️⃣ Handling Form Events (onChange & onSubmit)

import React, { useState } from 'react';

const FormExample = () => {
const [name, setName] = useState('');

const handleChange = (e) => {
setName(e.target.value);
};

const handleSubmit = (e) => {
e.preventDefault(); // Prevents page reload
alert(`Submitted: ${name}`);
};

return (
<form onSubmit={handleSubmit}>
<input type="text" value={name} onChange={handleChange} placeholder="Enter your name" />
<button type="submit">Submit</button>
</form>
);
};

export default FormExample;

🛠️ Key Points:

onChange captures input updates.
onSubmit handles form submission.
e.preventDefault() stops page reload.

4️⃣ Handling Keyboard Events (onKeyDown, onKeyUp)

const KeyboardExample = () => {
const handleKeyDown = (e) => {
if (e.key === 'Enter') {
alert('Enter key pressed! ⌨️');
}
};

return <input type="text" onKeyDown={handleKeyDown} placeholder="Press Enter" />;
};

export default KeyboardExample;

5️⃣ Handling Events in Class Components

import React, { Component } from 'react';

class ClassEventExample extends Component {
handleClick = () => {
alert('Class Button Clicked! 🏆');
};

render() {
return <button onClick={this.handleClick}>Click Me (Class)</button>;
}
}

export default ClassEventExample;

🛠️ Class Components:

Event handlers can be defined as class methods.
Use arrow functions to avoid manual binding or bind in the constructor.

🚀 Pro Tips:

Debounce or throttle frequent events like onScroll or onResize.
For complex forms, use libraries like Formik or React Hook Form.
Use e.stopPropagation() if you need to prevent event bubbling.

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Asked: February 20, 2025In: ReactJs

What is prop drilling and how do you avoid it?

Sarah Thompson Beginner

Added an answer on February 20, 2025 at 10:20 am

This answer was edited.

🔍 What is Prop Drilling? Prop Drilling happens when you pass props through multiple layers of components just to reach a deeply nested child. It can make the code messy and hard to maintain. 🚫 Example of Prop Drilling const App = () => { const user = "Kramer"; return <Parent user={user} />;Read more

🔍 What is Prop Drilling?

Prop Drilling happens when you pass props through multiple layers of components just to reach a deeply nested child. It can make the code messy and hard to maintain.

🚫 Example of Prop Drilling

const App = () => {
const user = "Kramer";

return <Parent user={user} />;
};

const Parent = ({ user }) => {
return <Child user={user} />;
};

const Child = ({ user }) => {
return <GrandChild user={user} />;
};

const GrandChild = ({ user }) => {
return <h2>Hello, {user}! 👋</h2>;
};

export default App;

⚡ Problem: The user prop is passed through Parent and Child just to reach GrandChild.

✅ How to Avoid Prop Drilling?

React Context API
State Management Libraries (Redux, Zustand)
Component Composition
useContext + useReducer combo for more complex state

🛠 Solution Using React Context API

import React, { createContext, useContext } from 'react';

// 1️⃣ Create Context
const UserContext = createContext();

const App = () => {
const user = "Kramer";

return (
// 2️⃣ Provide Context Value
<UserContext.Provider value={user}>
<Parent />
</UserContext.Provider>
);
};

const Parent = () => <Child />;

const Child = () => <GrandChild />;

const GrandChild = () => {
// 3️⃣ Consume Context
const user = useContext(UserContext);
return <h2>Hello, {user}! 🎉</h2>;
};

export default App;

⚡ Why This is Better?

No need to pass props manually through Parent and Child.
GrandChild directly consumes the user data using useContext.
Cleaner and more maintainable code!

🚀 Pro Tip:

For simple cases, Context API works great.
For larger apps, consider Redux or Zustand for advanced state management.

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What is React.memo?

🛠️ Basic Syntax:

🧩 Example Without React.memo (Unnecessary Re-renders):

✅ Optimized with React.memo:

⚡ When to Use React.memo?

⚠️ When NOT to Use React.memo?

🧠 Advanced: Using React.memo with areEqual Function

🚀 Pro Tip:

Redux vs. Context API in React

📊 High-Level Comparison

🛠️ Context API Example

🛠️ Redux Example

🚀 When to Use Context API?

🚀 When to Use Redux?

⚡ Pro Tip:

🆚 Client-Side Rendering vs. Server-Side Rendering

🚀 SSR with Next.js (Popular SSR Framework for React)

1️⃣ Setting Up Next.js

2️⃣ Example: SSR in Next.js

⚡ How It Works:

3️⃣ API Call Example in SSR

🌟 Why Use SSR?

🚫 When Not to Use SSR?

⚡ Pro Tip:

⚡ Handling Events in ReactJS

1️⃣ Handling Click Events

2️⃣ Passing Arguments to Event Handlers

3️⃣ Handling Form Events (onChange & onSubmit)

4️⃣ Handling Keyboard Events (onKeyDown, onKeyUp)

5️⃣ Handling Events in Class Components

🚀 Pro Tips:

🔍 What is Prop Drilling?

🚫 Example of Prop Drilling

✅ How to Avoid Prop Drilling?

🛠 Solution Using React Context API

⚡ Why This is Better?

🚀 Pro Tip:

What is `React.memo`?

🧩 Example Without `React.memo` (Unnecessary Re-renders):

✅ Optimized with `React.memo`:

⚡ When to Use `React.memo`?

⚠️ When NOT to Use `React.memo`?

🧠 Advanced: Using `React.memo` with `areEqual` Function