Introduction to React
React is a JavaScript library created by Facebook (now Meta) for building user interfaces. It was released in 2013 and has since become one of the most popular tools for creating web applications. React makes it easier to build complex websites by breaking them into small, reusable pieces called components.
Instead of rewriting entire web pages when something changes, React updates only the parts that need to change. This makes applications faster and more efficient.
What Problem Does React Solve?
Traditional websites update the entire page every time something changes. For example, if you like a post on a social media site, the old approach would reload the entire page just to update the like count. React solves this by tracking only the parts of a page that change and updating just those parts — nothing more.
Think of it like a whiteboard. Instead of erasing the whole board and redrawing everything, React erases only the small part that changed and redraws just that section.
What is a Library vs a Framework?
React is a library, not a full framework. This means React focuses on one thing — building user interfaces (the visual part of your app). You can combine React with other tools to handle things like routing (navigating between pages) or data management.
Compare this to something like Angular, which is a full framework that includes everything built-in. React gives you more flexibility but requires choosing additional tools as needed.
Where is React Used?
React is used to build the visible parts of web applications — buttons, menus, forms, dashboards, and more. Some well-known companies that use React include:
- Facebook and Instagram
- Netflix
- Airbnb
- Atlassian (Jira, Confluence)
- WhatsApp Web
How React Works — A Simple Analogy
Imagine a restaurant menu board. When a dish sells out, a staff member doesn't reprint the entire menu — they just update the one item that changed. React works the same way with web pages. It keeps a virtual copy of the page in memory (called the Virtual DOM), compares it to what is currently shown, and updates only the differences.
Key Concepts to Know Before Starting
Before diving deeper into React, it helps to have a basic understanding of the following:
- HTML — The structure of a web page
- CSS — The styling of a web page
- JavaScript (JS) — The logic that makes a page interactive
React is built on JavaScript, so knowledge of JavaScript basics such as variables, functions, arrays, and objects will make learning React much smoother.
What Will Be Covered in This Course?
This course is structured from beginner to advanced. Topics include:
- Setting up a React project
- Understanding JSX (React's special syntax)
- Building and using components
- Working with props and state
- Handling events and forms
- React Hooks (useState, useEffect, useContext, and more)
- Routing, performance optimization, and testing
Example — What a React Component Looks Like
Below is a simple React component that displays a greeting message. Do not worry if it looks unfamiliar — every part of this will be explained in upcoming topics.
function Greeting() {
return <h1>Hello, welcome to React!</h1>;
}
This small piece of code is a component. It is a JavaScript function that returns something that looks like HTML. This mix of JavaScript and HTML-like code is called JSX, and it is one of React's most powerful features.
Key Points
- React is a JavaScript library used for building user interfaces.
- It was created by Facebook and is widely used in modern web development.
- React updates only the parts of a page that change, making it efficient.
- The building blocks of a React application are called components.
- React uses a Virtual DOM to minimize direct changes to the actual webpage.
- Basic knowledge of HTML, CSS, and JavaScript is recommended before starting.
The next topic covers how to set up a React development environment so the first React application can be built and run locally.