React.js, often simply called React, is an extremely popular open-source JavaScript library developed by Facebook. It allows you to create interactive, dynamic, and high-performance user interfaces. Whether you are an experienced developer or just starting out in web application development, React is an excellent choice for building modern and responsive applications.
In this article, we will show you how to create a web application with React.js, step by step. By the end, you’ll be able to develop a functional application and better understand the fundamental concepts of React.
Why choose React.js for a web application?
Before diving into development, it’s important to understand why React.js is a great choice for building a web application:
Modularity: With React, you build your application using reusable components, which reduces code redundancy and makes it easier to maintain.
Performance: React uses a « virtual DOM » that improves the performance of UI updates by rendering only the changed elements.
Rich ecosystem: Thanks to a large community, React benefits from numerous tools, libraries, and extensions, making development easier.
Prerequisites before getting started
Before you start creating an application with React, you should have the following basic knowledge:
HTML, CSS, and JavaScript: A good understanding of these technologies is essential.
Node.js and npm: React uses Node.js to manage its development environment. npm (Node Package Manager) is used to install libraries and dependencies. If you haven’t installed Node.js yet, go to nodejs.org and download it. npm is included with Node.js, so you don’t need to install it separately.
Setting up the React development environment
React has a command-line tool called Create React App, which simplifies the configuration of a React project. To start a new React project, follow these steps:
Open your terminal and ensure that Node.js is installed by typing the following command:
If you see the versions of Node and npm, you are ready to continue.
Install Create React App if it’s not already installed:
Your application’s name should be a valid folder name.
Navigate to your project folder:
Start the development server:
This command launches your React application in your browser at http://localhost:3000. From there, you can start developing.
Understanding the structure of a React application
Once you’ve generated your project with Create React App, you’ll see several files and folders in your project. Here are the most important ones:
public/: Contains static files like the base HTML (index.html).
src/: This is where you’ll develop the majority of your application. This folder contains the App.js file, which is the entry point of your application.
node_modules/: Contains all dependencies installed via npm. Most of your development with React happens in the src folder.
Creating a React component
Components are the heart of React. Every part of your user interface can be broken down into individual, reusable components. A React component is a JavaScript function that returns JSX (a language that combines JavaScript and HTML).
Here’s how to create a simple component:
In the src/App.js file, replace the content with the following code:
Component structure:
The App component is a function that returns a piece of user interface (JSX). Each HTML tag in the function’s return represents an element of the user interface.
Managing state with useState
State management is essential in a dynamic web application. React provides the useState hook to manage a component’s state.
Let’s add a button to our application that, when clicked, updates a counter:
Modify the App.js file as follows:
Explanation:
useState is a hook that allows you to define and manipulate a state.
count represents the current state (in this case, the number of clicks).
setCount is a function used to update the state.
When the button is clicked, setCount is called to increment the counter value.
Making an API call with useEffect
To make your application more useful, you can integrate data from an API. Let’s use the useEffect hook to make an API call.
Add this modification to your App.js file to fetch external data:
Explanation:
useEffect allows you to perform side effects, such as API calls, after the component renders.
The fetch API call retrieves a post and displays it once the data is available.
Deploying your application
Once your application is ready, you can deploy it so it’s accessible on the web. You can use platforms like Netlify, Vercel, or GitHub Pages to deploy your application for free.
For Netlify, for example, you just need to link your GitHub repository to their platform, and your application will be published online automatically after every update.
Conclusion
React.js is a powerful library that allows you to create fast, dynamic, and modular web applications. By following the steps outlined in this article, you are now capable of building a React application, managing its state, calling APIs, and deploying it.
Feel free to deepen your knowledge by experimenting with more complex components, routing with React Router, or global state management solutions like Redux. Good luck with your React.js projects!