Full Stack Development – Important Questions and Answers

April 28, 2026

Full Stack Development – Important Questions and Answers

1. What is Virtual DOM in React?

Virtual DOM is a lightweight copy of the real DOM used by React to improve performance.

How it works:

React creates a virtual DOM in memory
Compares it with previous version (diffing)
Updates only changed parts in real DOM

Advantage:

Faster updates
Efficient rendering
Improved performance

2. Explain Props in React with example.

Props (Properties) are used to pass data from parent to child components.

Example:

function Welcome(props) {
  return <h1>Hello {props.name}</h1>;
}

<Welcome name="Kavita" />

Features:

Read-only
Used for communication between components

3. What is State in React and how is it different from Props?

State is used to manage dynamic data within a component.

Example:

import { useState } from "react";

function Counter() {
  const [count, setCount] = useState(0);
  return <button onClick={() => setCount(count + 1)}>{count}</button>;
}

Difference:

Props	State
Passed from parent	Managed inside component
Immutable	Mutable
Read-only	Can be updated

4. What are Node.js modules?

Modules are reusable blocks of code in Node.js.

Types:

Built-in modules (fs, http)
Custom modules

Example:

const fs = require('fs');

Advantage:

Code reusability
Better organization

5. Explain synchronous and asynchronous file operations in Node.js.

Synchronous:

Executes line by line
Blocks execution

const data = fs.readFileSync('file.txt', 'utf8');

Asynchronous:

Non-blocking
Faster execution

fs.readFile('file.txt', 'utf8', (err, data) => {
  console.log(data);
});

6. How do props and state work together in React?

Props pass data, while state manages dynamic changes.

Example:

function Child(props) {
  return <h1>{props.value}</h1>;
}

function Parent() {
  const [data, setData] = useState("Hello");
  return <Child value={data} />;
}

7. Create a simple React component using props and state.

import { useState } from "react";

function App() {
  const [name, setName] = useState("Student");

  return (
    <div>
      <h1>Hello {name}</h1>
      <button onClick={() => setName("Juhi")}>
        Change Name
      </button>
    </div>
  );
}

8. Explain working of Virtual DOM and compare with Real DOM.

Virtual DOM:

Stored in memory
Faster updates

Real DOM:

Directly manipulates UI
Slower performance

Comparison:

Feature	Virtual DOM	Real DOM
Speed	Fast	Slow
Updates	Partial	Full
Efficiency	High	Low

9. What is Redux in React?

Redux is a state management library.

Components:

Store
Actions
Reducers

Flow:

Action → Reducer → Store → UI

10. Explain Redux flow with example.

const reducer = (state = 0, action) => {
  if (action.type === "INCREMENT") {
    return state + 1;
  }
  return state;
};

Flow:

Dispatch action
Reducer updates state
Store holds updated state

11. What is React Router?

React Router is used for navigation between components.

Example:

import { BrowserRouter, Routes, Route } from "react-router-dom";

<BrowserRouter>
  <Routes>
    <Route path="/" element={<Home />} />
  </Routes>
</BrowserRouter>

12. How do Redux and Router work together in an application?

Redux manages global state
Router handles navigation

Example:

User logs in → Redux stores user → Router redirects to dashboard

13. What are REST API design principles?

REST APIs follow standard rules for communication.

Principles:

Stateless
Resource-based
Uses HTTP methods

14. Explain URI design in REST API.

URI represents a resource.

Example:

/api/students
/api/students/1

Rules:

Use nouns
Keep it simple

15. Explain HTTP methods in REST API.

Method	Purpose
GET	Retrieve data
POST	Create data
PUT	Update data
DELETE	Remove data

16. What is representation in REST API?

Representation is the format of data exchanged.

Formats:

JSON
XML

Example:

{
  "name": "Amit"
}

17. Create a simple Node.js web server.

const http = require('http');

const server = http.createServer((req, res) => {
  res.write("Hello World");
  res.end();
});

server.listen(3000);

18. How does Node.js handle HTTP requests?

Uses event-driven architecture
Handles multiple requests asynchronously

19. Demonstrate file handling in Node.js.

Write File:

fs.writeFile('test.txt', 'Hello', () => {});

Read File:

fs.readFile('test.txt', 'utf8', (err, data) => {
  console.log(data);
});

20. What is Angular architecture?

Angular is a frontend framework based on components.

Main parts:

Components
Modules
Services

21. Explain Angular components.

Components control UI.

Example:

@Component({
  selector: 'app-root',
  template: '<h1>Hello</h1>'
})

22. What is data binding in Angular?

Data binding connects UI and logic.

Types:

One-way
Two-way

Example:

<input [(ngModel)]="name">

23. Explain form validation in Angular.

Validation ensures correct user input.

Example:

<input required minlength="3">

Features:

Built-in validators
Custom validation