✅ React.js Essentials ⚛️🔥
React.js is a JavaScript library for building user interfaces, especially single-page apps. Created by Meta, it focuses on components, speed, and interactivity.
1️⃣ What is React?
React lets you build reusable UI components and update the DOM efficiently using a virtual DOM.
Why Use React?
• Reusable components
• Faster performance with virtual DOM
• Great for building SPAs (Single Page Applications)
• Strong community and ecosystem
2️⃣ Key Concepts
📦 Components – Reusable, independent pieces of UI.
🧠 Props – Pass data to components
💡 State – Store and manage data in a component
3️⃣ Hooks
useState – Manage local state
useEffect – Run side effects (like API calls, DOM updates)
4️⃣ JSX
JSX lets you write HTML inside JS.
5️⃣ Conditional Rendering
6️⃣ Lists and Keys
7️⃣ Event Handling
8️⃣ Form Handling
9️⃣ React Router (Bonus)
To handle multiple pages
🛠 Practice Tasks
✅ Build a counter
✅ Make a TODO app using state
✅ Fetch and display API data
✅ Try routing between 2 pages
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React.js is a JavaScript library for building user interfaces, especially single-page apps. Created by Meta, it focuses on components, speed, and interactivity.
1️⃣ What is React?
React lets you build reusable UI components and update the DOM efficiently using a virtual DOM.
Why Use React?
• Reusable components
• Faster performance with virtual DOM
• Great for building SPAs (Single Page Applications)
• Strong community and ecosystem
2️⃣ Key Concepts
📦 Components – Reusable, independent pieces of UI.
function Welcome() {
return <h1>Hello, React!</h1>;
}
🧠 Props – Pass data to components
function Greet(props) {
return <h2>Hello, {props.name}!</h2>;
}
<Greet name="Riya" />
💡 State – Store and manage data in a component
import { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
return (
<>
<p>Count: {count}</p>
<button onClick={() => setCount(count + 1)}>Add</button>
</>
);
}
3️⃣ Hooks
useState – Manage local state
useEffect – Run side effects (like API calls, DOM updates)
import { useEffect } from 'react';
useEffect(() => {
console.log("Component mounted");
}, []);
4️⃣ JSX
JSX lets you write HTML inside JS.
const element = <h1>Hello World</h1>;
5️⃣ Conditional Rendering
{isLoggedIn ? <Dashboard /> : <Login />}
6️⃣ Lists and Keys
const items = ["Apple", "Banana"];
items.map((item, index) => <li key={index}>{item}</li>);
7️⃣ Event Handling
<button onClick={handleClick}>Click Me</button>
8️⃣ Form Handling
<input value={name} onChange={(e) => setName(e.target.value)} />
9️⃣ React Router (Bonus)
To handle multiple pages
npm install react-router-dom
import { BrowserRouter, Route, Routes } from 'react-router-dom';
🛠 Practice Tasks
✅ Build a counter
✅ Make a TODO app using state
✅ Fetch and display API data
✅ Try routing between 2 pages
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✅ Web development Interview Questions with Answers Part-8
71. What is MVC architecture?
MVC separates concerns into three parts:
• Model: Handles data and business logic
• View: Handles UI
• Controller: Handles user input and flow
This separation improves maintainability and testing.
72. What is the difference between monolithic and microservices architecture?
Monolithic architecture is a single deployable unit, simpler to start with, but scales as a whole. Microservices architecture splits functionality into independent services, more complex, but scales independently. Choice depends on team size and complexity.
73. What is an API gateway and why is it used?
An API gateway:
• Sits between clients and services
• Handles routing, auth, rate limiting
• Simplifies client communication
• Centralizes cross-cutting concerns
74. What caching strategies do you use in web applications?
• Client-side caching for static assets
• Server-side caching for frequent queries
• CDN caching for global delivery
Cache invalidation is handled carefully.
75. What is a CDN and how does it help performance?
A CDN:
• Serves content from locations closer to users
• Reduces latency
• Reduces server load
• Improves global performance
76. What is load balancing?
Load balancing:
• Distributes traffic across servers
• Improves availability and fault tolerance
Common methods include round robin and least connections.
77. What is the difference between scalability and performance?
• Performance: Speed for a single request
• Scalability: Handling increased load
A fast system that fails under load is not scalable.
78. What is the difference between horizontal and vertical scaling?
• Vertical scaling: Adds more resources to a server
• Horizontal scaling: Adds more servers
Horizontal scaling is more resilient.
79. What is the difference between WebSockets and HTTP?
• HTTP: Request-response based
• WebSockets: Persistent, two-way communication
Use WebSockets for real-time features like chat.
80. How do you handle file uploads securely?
• Validate file type and size
• Rename files to prevent collisions
• Store files outside the public directory
• Scan files when required
Double Tap ♥️ For Part-9
71. What is MVC architecture?
MVC separates concerns into three parts:
• Model: Handles data and business logic
• View: Handles UI
• Controller: Handles user input and flow
This separation improves maintainability and testing.
72. What is the difference between monolithic and microservices architecture?
Monolithic architecture is a single deployable unit, simpler to start with, but scales as a whole. Microservices architecture splits functionality into independent services, more complex, but scales independently. Choice depends on team size and complexity.
73. What is an API gateway and why is it used?
An API gateway:
• Sits between clients and services
• Handles routing, auth, rate limiting
• Simplifies client communication
• Centralizes cross-cutting concerns
74. What caching strategies do you use in web applications?
• Client-side caching for static assets
• Server-side caching for frequent queries
• CDN caching for global delivery
Cache invalidation is handled carefully.
75. What is a CDN and how does it help performance?
A CDN:
• Serves content from locations closer to users
• Reduces latency
• Reduces server load
• Improves global performance
76. What is load balancing?
Load balancing:
• Distributes traffic across servers
• Improves availability and fault tolerance
Common methods include round robin and least connections.
77. What is the difference between scalability and performance?
• Performance: Speed for a single request
• Scalability: Handling increased load
A fast system that fails under load is not scalable.
78. What is the difference between horizontal and vertical scaling?
• Vertical scaling: Adds more resources to a server
• Horizontal scaling: Adds more servers
Horizontal scaling is more resilient.
79. What is the difference between WebSockets and HTTP?
• HTTP: Request-response based
• WebSockets: Persistent, two-way communication
Use WebSockets for real-time features like chat.
80. How do you handle file uploads securely?
• Validate file type and size
• Rename files to prevent collisions
• Store files outside the public directory
• Scan files when required
Double Tap ♥️ For Part-9
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🔰 Auto fill Pseudo Element in CSS
Default browser highlights in auto-filled fields can clash with a site’s design. By leveraging the
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Default browser highlights in auto-filled fields can clash with a site’s design. By leveraging the
:-webkit-autofill pseudo-class, developers can override these styles and ensure consistent branding across modern browsers.@CodingCoursePro
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✅ Web development Interview Questions with Answers: Part-1
QUESTION 1
What happens step by step when you enter a URL in a browser and press Enter?
Answer
You trigger a long chain of events.
• Browser parses the URL and identifies protocol, domain, path
• Browser checks cache, DNS cache, OS cache, router cache
• If not found, DNS lookup happens to get the IP address
• Browser opens a TCP connection with the server
• HTTPS triggers TLS handshake for encryption
• Browser sends an HTTP request to the server
• Server processes request and sends HTTP response
• Browser downloads HTML, CSS, JS, images
• HTML parsed into DOM
• CSS parsed into CSSOM
• DOM + CSSOM create render tree
• Layout calculates positions
• Paint draws pixels on screen
• JavaScript executes and updates UI
Interview tip
Mention DNS, TCP, TLS, render tree. This separates juniors from seniors.
QUESTION 2
What are the roles of HTML, CSS, and JavaScript in a web application?
Answer
Each layer has a single responsibility.
HTML
• Structure of the page
• Content and meaning
• Headings, forms, inputs, buttons
CSS
• Presentation and layout
• Colors, fonts, spacing
• Responsive behavior
JavaScript
• Behavior and logic
• Events, API calls, validation
• Dynamic updates
Real example
HTML builds a login form
CSS styles it
JavaScript validates input and sends API request
QUESTION 3
What are the main differences between HTML and HTML5?
Answer
HTML5 added native capabilities.
Key differences
• Semantic tags like header, footer, article
• Audio and video support without plugins
• Canvas and SVG for graphics
• Local storage and session storage
QUESTION 4
What is the difference between block-level and inline elements in HTML?
Answer
Block elements
• Start on a new line
• Take full width
• Respect height and width
• Examples: div, p, h1
Inline elements
• Stay in same line
• Take only content width
• Height and width ignored
• Examples: span, a, strong
Inline-block
• Stays inline
• Respects height and width
QUESTION 5
What is semantic HTML and why is it important for SEO and accessibility?
Answer
Semantic HTML uses meaningful tags.
Examples
• header, nav, main, article, section, footer
Benefits
• Search engines understand content better
• Screen readers read pages correctly
• Code becomes readable and maintainable
SEO example
article tag signals main content to search engines.
Accessibility example
Screen readers jump between landmarks.
QUESTION 6
What are meta tags and how do they impact search engines?
Answer
Meta tags provide page metadata.
Common meta tags
• charset defines encoding
• viewport controls responsiveness
• denoscription influences search snippets
• robots control indexing
SEO impact
• Denoscription affects click-through rate
• Robots tag controls indexing behavior
Note: Meta keywords are ignored by modern search engines.
QUESTION 7
What is the difference between class and id attributes in HTML?
Answer
ID
• Unique
• Used once per page
• High CSS specificity
• Used for anchors and JS targeting
Class
• Reusable
• Applied to multiple elements
• Preferred for styling
QUESTION 8
What is a DOCTYPE declaration and why is it required?
Answer
DOCTYPE tells the browser how to render the page.
Without DOCTYPE
• Browser enters quirks mode
• Layout breaks
• Inconsistent behavior
With DOCTYPE
• Standards mode
• Predictable rendering
QUESTION 9
How do HTML forms work and what are common input types?
Answer
Forms collect and send user data.
Process
• User fills inputs
• Submit triggers request
• Data sent via GET or POST
Common input types
• text, email, password
• number, date
• radio, checkbox
• file
Security note
Always validate on server side.
QUESTION 10
What is web accessibility and what are ARIA roles used for?
Answer
Accessibility ensures usable web apps for everyone.
Who benefits
• Screen reader users
• Keyboard users
• Users with visual or motor impairments
ARIA roles
• Add meaning when native HTML falls short
• role, aria-label, aria-hidden
Rule
Use semantic HTML first. Use ARIA only when needed.
Double Tap ♥️ For Part-2
QUESTION 1
What happens step by step when you enter a URL in a browser and press Enter?
Answer
You trigger a long chain of events.
• Browser parses the URL and identifies protocol, domain, path
• Browser checks cache, DNS cache, OS cache, router cache
• If not found, DNS lookup happens to get the IP address
• Browser opens a TCP connection with the server
• HTTPS triggers TLS handshake for encryption
• Browser sends an HTTP request to the server
• Server processes request and sends HTTP response
• Browser downloads HTML, CSS, JS, images
• HTML parsed into DOM
• CSS parsed into CSSOM
• DOM + CSSOM create render tree
• Layout calculates positions
• Paint draws pixels on screen
• JavaScript executes and updates UI
Interview tip
Mention DNS, TCP, TLS, render tree. This separates juniors from seniors.
QUESTION 2
What are the roles of HTML, CSS, and JavaScript in a web application?
Answer
Each layer has a single responsibility.
HTML
• Structure of the page
• Content and meaning
• Headings, forms, inputs, buttons
CSS
• Presentation and layout
• Colors, fonts, spacing
• Responsive behavior
JavaScript
• Behavior and logic
• Events, API calls, validation
• Dynamic updates
Real example
HTML builds a login form
CSS styles it
JavaScript validates input and sends API request
QUESTION 3
What are the main differences between HTML and HTML5?
Answer
HTML5 added native capabilities.
Key differences
• Semantic tags like header, footer, article
• Audio and video support without plugins
• Canvas and SVG for graphics
• Local storage and session storage
QUESTION 4
What is the difference between block-level and inline elements in HTML?
Answer
Block elements
• Start on a new line
• Take full width
• Respect height and width
• Examples: div, p, h1
Inline elements
• Stay in same line
• Take only content width
• Height and width ignored
• Examples: span, a, strong
Inline-block
• Stays inline
• Respects height and width
QUESTION 5
What is semantic HTML and why is it important for SEO and accessibility?
Answer
Semantic HTML uses meaningful tags.
Examples
• header, nav, main, article, section, footer
Benefits
• Search engines understand content better
• Screen readers read pages correctly
• Code becomes readable and maintainable
SEO example
article tag signals main content to search engines.
Accessibility example
Screen readers jump between landmarks.
QUESTION 6
What are meta tags and how do they impact search engines?
Answer
Meta tags provide page metadata.
Common meta tags
• charset defines encoding
• viewport controls responsiveness
• denoscription influences search snippets
• robots control indexing
SEO impact
• Denoscription affects click-through rate
• Robots tag controls indexing behavior
Note: Meta keywords are ignored by modern search engines.
QUESTION 7
What is the difference between class and id attributes in HTML?
Answer
ID
• Unique
• Used once per page
• High CSS specificity
• Used for anchors and JS targeting
Class
• Reusable
• Applied to multiple elements
• Preferred for styling
QUESTION 8
What is a DOCTYPE declaration and why is it required?
Answer
DOCTYPE tells the browser how to render the page.
Without DOCTYPE
• Browser enters quirks mode
• Layout breaks
• Inconsistent behavior
With DOCTYPE
• Standards mode
• Predictable rendering
QUESTION 9
How do HTML forms work and what are common input types?
Answer
Forms collect and send user data.
Process
• User fills inputs
• Submit triggers request
• Data sent via GET or POST
Common input types
• text, email, password
• number, date
• radio, checkbox
• file
Security note
Always validate on server side.
QUESTION 10
What is web accessibility and what are ARIA roles used for?
Answer
Accessibility ensures usable web apps for everyone.
Who benefits
• Screen reader users
• Keyboard users
• Users with visual or motor impairments
ARIA roles
• Add meaning when native HTML falls short
• role, aria-label, aria-hidden
Rule
Use semantic HTML first. Use ARIA only when needed.
Double Tap ♥️ For Part-2
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Cleanlab helps you clean data and labels by automatically detecting issues in a ML dataset.
A Python library that enables you to train, test, and evaluate multiple ML models at once using just a few lines of code.
A Python library for quickly visualizing and analyzing data, providing an easy and efficient way to explore data.
A time-saving tool that helps in importing all the necessary data science libraries and functions with a single line of code.
PivotTableJS lets you interactively analyse your data in Jupyter Notebooks without any code 🔥
Drawdata is a python library that allows you to draw a 2-D dataset of any shape in a Jupyter Notebook.
The Uncompromising Code Formatter
An open-source, low-code machine learning library in Python that automates the machine learning workflow.
Streamlines your model training, automates boilerplate code, and lets you focus on what matters: research & innovation.
🔟 Streamlit
A framework for creating web applications for data science and machine learning projects, allowing for easy and interactive data viz & model deployment.
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Don't overwhelm to learn Git,🙌
Git is only this much👇😇
1.Core:
• git init
• git clone
• git add
• git commit
• git status
• git diff
• git checkout
• git reset
• git log
• git show
• git tag
• git push
• git pull
2.Branching:
• git branch
• git checkout -b
• git merge
• git rebase
• git branch --set-upstream-to
• git branch --unset-upstream
• git cherry-pick
3.Merging:
• git merge
• git rebase
4.Stashing:
• git stash
• git stash pop
• git stash list
• git stash apply
• git stash drop
5.Remotes:
• git remote
• git remote add
• git remote remove
• git fetch
• git pull
• git push
• git clone --mirror
6.Configuration:
• git config
• git global config
• git reset config
7. Plumbing:
• git cat-file
• git checkout-index
• git commit-tree
• git diff-tree
• git for-each-ref
• git hash-object
• git ls-files
• git ls-remote
• git merge-tree
• git read-tree
• git rev-parse
• git show-branch
• git show-ref
• git symbolic-ref
• git tag --list
• git update-ref
8.Porcelain:
• git blame
• git bisect
• git checkout
• git commit
• git diff
• git fetch
• git grep
• git log
• git merge
• git push
• git rebase
• git reset
• git show
• git tag
9.Alias:
• git config --global alias.<alias> <command>
10.Hook:
• git config --local core.hooksPath <path>
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Git is only this much👇😇
1.Core:
• git init
• git clone
• git add
• git commit
• git status
• git diff
• git checkout
• git reset
• git log
• git show
• git tag
• git push
• git pull
2.Branching:
• git branch
• git checkout -b
• git merge
• git rebase
• git branch --set-upstream-to
• git branch --unset-upstream
• git cherry-pick
3.Merging:
• git merge
• git rebase
4.Stashing:
• git stash
• git stash pop
• git stash list
• git stash apply
• git stash drop
5.Remotes:
• git remote
• git remote add
• git remote remove
• git fetch
• git pull
• git push
• git clone --mirror
6.Configuration:
• git config
• git global config
• git reset config
7. Plumbing:
• git cat-file
• git checkout-index
• git commit-tree
• git diff-tree
• git for-each-ref
• git hash-object
• git ls-files
• git ls-remote
• git merge-tree
• git read-tree
• git rev-parse
• git show-branch
• git show-ref
• git symbolic-ref
• git tag --list
• git update-ref
8.Porcelain:
• git blame
• git bisect
• git checkout
• git commit
• git diff
• git fetch
• git grep
• git log
• git merge
• git push
• git rebase
• git reset
• git show
• git tag
9.Alias:
• git config --global alias.<alias> <command>
10.Hook:
• git config --local core.hooksPath <path>
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Happy Republic Day.
Warm regards by #TheStarkArmy
On this Special Day we have decided to give 10% off on all Premium channel
And 15% off on buying all 7 Premium channels at once
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✅ CSS3 Basics You Should Know 🎨🖥
CSS3 (Cascading Style Sheets – Level 3) controls the look and feel of your HTML pages. Here's what you need to master:
1️⃣ Selectors – Target Elements
Selectors let you apply styles to specific HTML parts:
2️⃣ Box Model – Understand Layout
Every element is a box with:
• Content → text/image inside
• Padding → space around content
• Border → around the padding
• Margin → space outside border
3️⃣ Flexbox – Align with Ease
Great for centering or laying out elements:
4️⃣ Grid – 2D Layout Power
Use when you need rows and columns:
5️⃣ Responsive Design – Mobile Friendly
Media queries adapt to screen size:
6️⃣ Styling Forms Buttons
Make UI friendly:
7️⃣ Transitions Animations
Add smooth effects:
🛠 Practice Task:
Build a card component using Flexbox:
• Title, image, denoscription, button
• Make it responsive on small screens
---
✅ CSS3 Basics + Real Interview Questions Answers 🧠📋
1️⃣ Q: What is CSS and why is it important?
A: CSS (Cascading Style Sheets) controls the visual presentation of HTML elements—colors, layout, fonts, spacing, and more.
2️⃣ Q: What’s the difference between id and class in CSS?
A:
• #id targets a unique element
• .class targets multiple elements
→ Use id for one-time styles, class for reusable styles.
3️⃣ Q: What is the Box Model in CSS?
A: Every HTML element is a box with:
• content → actual text/image
• padding → space around content
• border → edge around padding
• margin → space outside the border
4️⃣ Q: What are pseudo-classes?
A: Pseudo-classes define a special state of an element. Examples:
5️⃣ Q: What is the difference between relative, absolute, and fixed positioning?
A:
• relative → positioned relative to itself
• absolute → positioned relative to nearest positioned ancestor
• fixed → positioned relative to viewport
6️⃣ Q: What is Flexbox used for?
A: Flexbox is a layout model that arranges items in rows or columns, making responsive design easier.
7️⃣ Q: How do media queries work?
A: Media queries apply styles based on device characteristics like screen width, height, or orientation.
CSS3 (Cascading Style Sheets – Level 3) controls the look and feel of your HTML pages. Here's what you need to master:
1️⃣ Selectors – Target Elements
Selectors let you apply styles to specific HTML parts:
p { color: blue; } /* targets all <p> tags */
#noscript { font-size: 24px; } /* targets ID "noscript" */
.card { padding: 10px; } /* targets class "card" */2️⃣ Box Model – Understand Layout
Every element is a box with:
• Content → text/image inside
• Padding → space around content
• Border → around the padding
• Margin → space outside border
div {
padding: 10px;
border: 1px solid black;
margin: 20px;
}3️⃣ Flexbox – Align with Ease
Great for centering or laying out elements:
.container {
display: flex;
justify-content: center; /* horizontal */
align-items: center; /* vertical */
}4️⃣ Grid – 2D Layout Power
Use when you need rows and columns:
.grid {
display: grid;
grid-template-columns: 1fr 2fr;
gap: 20px;
}5️⃣ Responsive Design – Mobile Friendly
Media queries adapt to screen size:
@media (max-width: 768px) {
.card { font-size: 14px; }
}6️⃣ Styling Forms Buttons
Make UI friendly:
input {
border: none;
padding: 8px;
border-radius: 4px;
}
button {
background-color: #4CAF50;
color: white;
border: none;
padding: 10px;
}7️⃣ Transitions Animations
Add smooth effects:
.button {
transition: background-color 0.3s ease;
}
.button:hover {
background-color: #333;
}🛠 Practice Task:
Build a card component using Flexbox:
• Title, image, denoscription, button
• Make it responsive on small screens
---
✅ CSS3 Basics + Real Interview Questions Answers 🧠📋
1️⃣ Q: What is CSS and why is it important?
A: CSS (Cascading Style Sheets) controls the visual presentation of HTML elements—colors, layout, fonts, spacing, and more.
2️⃣ Q: What’s the difference between id and class in CSS?
A:
• #id targets a unique element
• .class targets multiple elements
→ Use id for one-time styles, class for reusable styles.
3️⃣ Q: What is the Box Model in CSS?
A: Every HTML element is a box with:
• content → actual text/image
• padding → space around content
• border → edge around padding
• margin → space outside the border
4️⃣ Q: What are pseudo-classes?
A: Pseudo-classes define a special state of an element. Examples:
:hover, :first-child, :nth-of-type()5️⃣ Q: What is the difference between relative, absolute, and fixed positioning?
A:
• relative → positioned relative to itself
• absolute → positioned relative to nearest positioned ancestor
• fixed → positioned relative to viewport
6️⃣ Q: What is Flexbox used for?
A: Flexbox is a layout model that arranges items in rows or columns, making responsive design easier.
7️⃣ Q: How do media queries work?
A: Media queries apply styles based on device characteristics like screen width, height, or orientation.