Originally published on CodingCush.
React is a free JavaScript library for building user interfaces, the parts of a website or app that people actually see and click. Instead of writing one giant page of code, you build small reusable pieces called components, like buttons, cards, menus and forms, and React puts them together on the screen. You describe what the screen should look like, and React updates it automatically when your data changes. That simple idea is why React powers so many modern websites, from small blogs to huge social networks.
A Short History: Where Did React Come From?
React was created by Meta, the company behind Facebook and Instagram. Engineers there were struggling to keep a fast-growing interface in sync, and updating everything by hand was slow and full of bugs. React was released in 2013, and other developers quickly adopted it.
Today React is open source, so anyone can use it for free. A huge community builds tools and tutorials around it, so when you get stuck, someone has almost certainly solved the same problem before.
The Big Idea: Components
Think of a page like Lego bricks. A header is one brick, a product card another, a footer another. In React, each brick is a component: a small JavaScript function that returns markup for that piece.
Components are reusable. Build a Button once and use it ten times with different text and colours. Build a ProductCard once and show fifty products without copying fifty blocks of HTML. Change the component in one place, and every copy updates.
If this idea is new to you, our guide to React components, props and state walks through it slowly with more examples, so keep that open in another tab while you practise.
Your First React Component
Here is a tiny but complete React component. It shows a greeting and a button that counts how many times you click it:
import { useState } from 'react'; function Counter() { const [count, setCount] = useState(0); return ( <div> <h2>Hello from React!</h2> <p>You clicked {count} times.</p> <button onClick={() => setCount(count + 1)}> Click me </button> </div> ); } export default Counter; The function returns markup that looks like HTML. The {count} part inserts a JavaScript value into that markup. When you click the button, setCount changes the value, and React redraws just that piece with the new number. You never wrote code to find and rewrite the paragraph by hand.
That strange HTML-inside-JavaScript syntax has a name: JSX. JSX lets you write markup inside your JavaScript files, which feels odd for about a day and then feels completely natural. Under the hood, tools convert JSX into regular JavaScript before the browser runs it.
The official React documentation (react.dev) — the Quick Start page creates a first component in a few lines.
Props and State: Passing Data and Remembering Things
Two words you will hear every day in React are props and state. Props are inputs passed from a parent component to a child, like passing ingredients to a chef. A ProductCard might receive a name, a price and an image as props, and simply display them. Props flow one way, from parent to child, which makes data easy to follow.
State is data a component remembers and can change: whether a menu is open, what a user typed, or the click count above. When state changes, React re-renders the component. Props are given to a component; state is owned by it.
The best way to learn both is by building. The official tutorial at react.dev/learn teaches components, props and state step by step with interactive examples you can edit in the browser, so you see results instantly without installing anything.
Declarative UI: Describe the Result, Not the Steps
React uses a declarative style. Declarative means you describe what the interface should look like for a given state, instead of listing every step to change it. Compare these two approaches for a loading spinner. In plain JavaScript you might write: find the spinner element, show it, find the button, disable it, and later remember to reverse all of that. In React you write something like: if loading is true, show the spinner and disable the button.
Your code becomes a description of the screen at any moment, rather than a diary of changes. That makes interfaces easier to predict and debug: when something looks wrong, you check the state, because the screen is simply a reflection of it.
What Is the Virtual DOM?
You will often hear that React is fast because of the virtual DOM. Here is the plain version. The DOM is the browser's live model of your page. Changing it directly, again and again, can be slow. React keeps a lightweight copy of the page structure in memory, called the virtual DOM.
When state changes, React updates this copy, compares it with the previous copy, and applies only the smallest real changes to the actual page. If one price on a page of fifty products changes, React updates that one price instead of rebuilding the whole list.
React vs Plain JavaScript
React is still JavaScript, so why not skip it? For tiny pages, plain JavaScript is perfectly fine. As an app grows, though, keeping the screen and the data in sync by hand becomes painful. This table sums up the difference:
| Feature | Plain JavaScript | React |
|---|---|---|
| Building the UI | You create and update elements manually | You build reusable components |
| Updating the screen | You find elements and change them yourself | React updates the screen when state changes |
| Reusing code | Copy and paste, or custom functions | Components are reused by design |
| Code organisation | Can get messy in large apps | Each component keeps its markup and logic together |
| Learning curve | Nothing extra to learn | Needs JSX, props, state and hooks |
| Best for | Small pages and simple effects | Interactive apps with lots of changing data |
Neither side wins everywhere. React earns its place when an interface has many moving parts that depend on shared, changing data.
Where Is React Used?
React runs parts of Facebook, Instagram and countless dashboards, shops and streaming sites. Companies like it because it is fast, well supported and easy to hire for.
React also reaches beyond the browser. React Native uses the same component ideas to build real mobile apps for Android and iOS, so learning React opens a door to app development too. Frameworks such as Next.js build on top of React, adding routing, server rendering and better search engine support for public websites. You can explore what the library offers on the homepage at react.dev, which links to the docs, the blog and the community resources.
Who Should Learn React, and What Comes First?
Learn React if you want to build modern web apps, apply for front-end jobs, or create projects like dashboards and online stores. Job listings ask for React constantly.
But do not start with React on day one. First learn HTML, CSS and JavaScript, especially functions, arrays, objects and methods like map and filter. Weak JavaScript makes React feel twice as hard. Our step-by-step beginner roadmap for learning React lays out the order to follow, week by week.
A good first project is a to-do list, a weather app using a free API, or a small shop page with a working cart. Keep projects small and finish them. Finishing beats perfect, every single time.
Frequently Asked Questions
Is React a language or a framework?
React is a JavaScript library, not a language and, strictly speaking, not a full framework. It focuses on the user interface. You add other tools for routing, data fetching and styling as your app needs them, or use a framework like Next.js that bundles those choices for you.
Is React hard for beginners?
React is beginner-friendly if your JavaScript basics are ready. JSX and state take a few days to feel normal. Most confusion comes from shaky JavaScript, not from React itself, so strengthen functions, arrays and objects first and React will click much faster.
Is React free to use?
Yes. React is completely free and open source under the MIT licence. You can use it for personal projects, client work and commercial products without paying anything, and the official documentation and community resources are free as well.
Can I build mobile apps with React?
Yes, through React Native. It uses React components and JavaScript to build genuine Android and iOS apps from one codebase. The concepts you learn for the web, like components, props and state, transfer directly, which makes it a popular next step after web React.
Conclusion
React is a JavaScript library for building interfaces from small, reusable components. You describe what the screen should look like, keep changing data in state, pass data down with props, and let React update the page efficiently for you. Learn HTML, CSS and JavaScript first, then build tiny projects one at a time. Start small today, and the components will soon start making sense.
