How to Create a Functional Calculator in React

Introduction to React Calculator

Creating a functional calculator in React is an excellent way to enhance your skills in this popular JavaScript library. This guide will walk you through the essential steps to build a simple yet effective calculator application.

Setting Up the Project

To start, you need to set up your React project. You can easily do this using Create React App with Vite. Open your terminal and run the

$ npm create vite@latest

Select as React from the following list and and install it.

App.jsx

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

const App = () => {
  const [display, setDisplay] = useState("");

  const handleClick = (value) => {
    if (value === "=") {
      try {
        setDisplay(eval(display).toString()); // Be cautious using eval in production
      } catch {
        setDisplay("Error");
      }
    } else if (value === "C") {
      setDisplay("");
    } else {
      setDisplay(display + value);
    }
  };

  const buttons = [
    "C", // "C" will be styled to span the entire width
    "7", "8", "9", "/",
    "4", "5", "6", "*",
    "1", "2", "3", "-",
    "0", ".", "=", "+"
  ];

  return (
    <div className="calculator">
      <div className="display">{display || "0"}</div>
      <div className="buttons">
        {buttons.map((btn, index) => (
          <button
            key={index}
            onClick={() => handleClick(btn)}
            className={btn === "C" ? "clear" : btn === "=" ? "equals" : ["+", "-", "*", "/"].includes(btn) ? "operator" : ""}
          >
            {btn}
          </button>
        ))}
      </div>
    </div>
  );
};

export default App;

App.css

/* General styles */body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(to top, #6a11cb, #2575fc);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator {
  background: #1e1e2f;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 15px 35px rgba(0, 0, 0, 0.7);
  width: 320px;
  display: flex;
  flex-direction: column;
}

.display {
  background: #282c34;
  color: #eaeaea;
  padding: 15px;
  font-size: 2rem;
  text-align: right;
  border-bottom: 2px solid #4a4e69;
  border-top-left-radius: 16px;
  border-top-right-radius: 16px;
  overflow: hidden;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  padding: 10px;
}

button {
  background: #4a4e69;
  color: #eaeaea;
  border: none;
  border-radius: 8px;
  font-size: 1.5rem;
  padding: 15px;
  cursor: pointer;
  transition: background 0.3s, transform 0.2s;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
  -webkit-transition: background 0.3s, transform 0.2s;
  -moz-transition: background 0.3s, transform 0.2s;
  -ms-transition: background 0.3s, transform 0.2s;
  -o-transition: background 0.3s, transform 0.2s;
}

button:hover {
  background: #5c5f77;
  transform: translateY(-2px);
}

button:active {
  transform: translateY(2px);
}

button.operator {
  background: #9c27b0;
  color: white;
}

button.operator:hover {
  background: #8e24aa;
}

button.operator:active {
  background: #7b1fa2;
}

button.clear {
  background: #e53935;
  color: white;
  grid-column: span 4; /* Full width */}

button.clear:hover {
  background: #c62828;
}

button.clear:active {
  background: #b71c1c;
}

button.equals {
  background: #4caf50;
  color: white;
}

button.equals:hover {
  background: #388e3c;
}

button.equals:active {
  background: #2e7d32;
}