Create a Counter App in React.js step by step. In this example, we’ll create a simple app that allows you to increment and decrement a counter value. Make sure you have Node.js and npm (Node Package Manager) installed on your system.

Step 1: Set Up Your Project Open your terminal and follow these commands:

npx create-react-app counter-app
cd counter-app
npm start

This will create a new React app called “counter-app,” navigate you into the project directory, and start the development server.

Step 2: Modify App Component Open the src/App.js file and replace its content with the following code:

import React, { useState } from 'react';
import './App.css';

function App() {
  const [count, setCount] = useState(0);

  const increment = () => {
    setCount(count + 1);
  };

  const decrement = () => {
    setCount(count - 1);
  };

  return (
    <div className="App">
      <h1>Counter App</h1>
      <div className="counter">
        <button onClick={decrement}>-</button>
        <span>{count}</span>
        <button onClick={increment}>+</button>
      </div>
    </div>
  );
}

export default App;

Step 3: Add Styling Open the src/App.css file and add some basic styling to make the app look better:

.App {
  text-align: center;
  margin-top: 50px;
}

.counter {
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 20px;
}

.counter button {
  font-size: 20px;
  padding: 10px 20px;
  margin: 0 10px;
  cursor: pointer;
  border: none;
  background-color: #007bff;
  color: #fff;
  border-radius: 5px;
}

.counter button:hover {
  background-color: #0056b3;
}

Step 4: Run the App With the above code in place, save your files and go back to the terminal. Make sure you’re still in the counter-app directory. If the development server isn’t running already, start it using:

npm start

Your browser should automatically open, displaying your Counter App. You can now increment and decrement the counter using the buttons.

That’s it! You’ve successfully created a simple Counter App using React.js. You can further customize and expand this app by adding features like maximum and minimum limits, styling improvements, animations, and more.