React Introduction

Kickstart React: Basics, Benefits, and Key Concepts

Learning Outcome

5

Identify key features, pros, and cons of React

4

Understand declarative vs imperative approach

3

Differentiate SPA vs MPA

2

Know why React is used in modern web apps

1

Understand what React is

Our Web Design Journey So Far

Before learning React, we have already covered:

HTML: Defines the structure and content of a webpage.

CSS: Controls the styling and visual appearance of a webpage.

JavaScript: Adds behavior and interactivity to a webpage.

Imagine a restaurant menu displayed on a digital screen.

As updates increase:

Mistakes happen

Updates become slow

Managing UI becomes difficult

Staff must manually update each section of the screen.

Whenever:

  • Item price changes

  • Offer starts

  • Item becomes unavailable

 This is exactly how plain JavaScript UI updates work in large apps — manual and hard to manage.

WHY is UI hard to manage with JavaScript as apps grow?

Developers control UI step by step

DOM updates are manual

Code becomes complex and messy

React solves this by:

  • Letting developers describe what UI should look like

  • Automatically updating UI when data changes

This shift is called Declarative UI

What is React?

React is a JavaScript library for building user interfaces

Created by Facebook (Meta)

Mainly used to build Single Page Applications (SPA)

Why React?

Earlier, when we built websites using HTML and JavaScript,
we created multiple pages.

This is called MPA (Multi Page Application)

In MPA:

  • Every click loads a new page

  • Page reload happens again and again
  • So the website feels slow

Too many page reloads = bad user experience

Why React?

So what is the solution?

That solution is SPA (Single Page Application).

In SPA (Using React):

  • The app loads only once

  • React updates only the UI

  • No page reload

  • Website feels fast and smooth

React builds SPA without reloads

MPA reloads pages

Key Features + Pros & Cons

Features:

  • Component-based structure

  • Reusable UI

  • Virtual DOM

  • Declarative approach

Pros:

  • Fast UI updates

  • Clean code

  • Easy maintenance

Cons:

  • Initial learning curve

  • Needs extra tools (router, state)

     

 Imperative vs Declarative

Why Declarative is Better

Less code

Fewer bugs

Easier to read

Scales better

Declarative (React):

Tell React what UI should look like

React handles updates

Change data → UI updates automatically

Imperative (JavaScript):

Tell browser how to update UI

Manual DOM changes

Summary

3

Ideal for modern, fast web applications

2

Focuses on what UI should be, not how to update it

1

React simplifies UI development

Quiz

React mainly helps in building

A. Static websites

B. Multi-page apps

C. Single Page Applications

D. Server-side apps

Quiz-Answer

React mainly helps in building

A. Static websites

B. Multi-page apps

C. Single Page Applications

D. Server-side apps

Copy of React - Kickstart React

By Content ITV

Copy of React - Kickstart React

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