JavaScript Application To Check Prime and Non-Prime Number

Last Updated : 06 Jan, 2025

Prime numbers have been a fundamental concept in mathematics and computer science. In programming, checking if a number is prime will help to understand loops, conditions, and optimization techniques.

What We Are Going to Create

We will create a simple web application where users can input a number to check if it’s a Prime or Non-Prime number. The application will:

Accept a number as input from the user.
Check whether the number is prime or non-prime.
Display the result to the user.

Project Preview

Prime and Non-Prime Number - HTML & CSS Structure

This structure provides a simple web interface with an input field to enter a number and a button to check whether the number is prime or non-prime

HTML

<html>
<head>
    <title>Prime Number Checker</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            margin: 0;
            background-color: #f4f4f9;
        }

        .container {
            text-align: center;
            background: white;
            padding: 20px;
            border-radius: 10px;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
        }

        input {
            padding: 10px;
            width: 200px;
            margin: 10px 0;
            border: 1px solid #ccc;
            border-radius: 5px;
        }

        button {
            padding: 10px 20px;
            background-color: #4CAF50;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }

        button:hover {
            background-color: #45a049;
        }

        #result {
            margin-top: 20px;
            font-size: 18px;
        }
    </style>
</head>
<body>
    <div class="container">
        <h1>Prime Number Checker</h1>
        <input type="number" id="input" placeholder="Enter a number">
        <button onclick="cPrime()">Check</button>
        <p id="result"></p>
    </div>
</body>
</html>

In this example

body: Uses Flexbox to center content both vertically and horizontally, with a light gray background and no margins.
.container: A white box with rounded corners, padding, and a shadow for a card-like appearance.
input: Styled for usability with padding, a defined width, light border, and rounded corners.
button: Green background, white text, rounded corners, and a hover effect for better interaction.
#result: Displays output with spacing and a larger font size for visibility.

Prime and Non-Prime Number - JavaScript Functionality

The JavaScript function checks if a number is prime by iterating from 2 to the square root of the number. If the number is divisible by any value in this range, it's marked as non-prime otherwise, it is prime.

JavaScript

function cPrime() {
    const n = parseInt(document.getElementById('input').value);
    const res = document.getElementById('result');
    if (isNaN(n) || n <= 1) {
        res.textContent = "Please enter a number greater than 1.";
        res.style.color = "red";
        return;
    }
    let isPrime = true;
    for (let i = 2; i <= Math.sqrt(n); i++) {
        if (n % i === 0) {
            isPrime = false;
            break;
        }
    }
    if (isPrime) {
        res.textContent = `${n} is a Prime Number.`;
        res.style.color = "green";
    } else {
        res.textContent = `${n} is a Non-Prime Number.`;
        res.style.color = "blue";
    }
}

In this example

The function retrieves the user input as a number from an input field with the ID input.
It checks if the input is valid (a number greater than 1); otherwise, it displays an error message in red.
A flag variable isPrime is initialized as true to track if the number is prime.
A for loop iterates from 2 to the square root of the input number to check divisibility. If any divisor is found, isPrime is set to false and the loop breaks.
If the number is prime, a success message is displayed in green; otherwise, a non-prime message is shown in blue.
The result is dynamically updated in an element with the ID result.

Complete Code

HTML

<html>
<head>
    <title>Prime Number Checker</title>
    <style>
        body {
            font-family: Arial, sans-serif;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            margin: 0;
            background-color: #f4f4f9;
        }

        .container {
            text-align: center;
            background: white;
            padding: 20px;
            border-radius: 10px;
            box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
        }

        input {
            padding: 10px;
            width: 200px;
            margin: 10px 0;
            border: 1px solid #ccc;
            border-radius: 5px;
        }

        button {
            padding: 10px 20px;
            background-color: #4CAF50;
            color: white;
            border: none;
            border-radius: 5px;
            cursor: pointer;
        }

        button:hover {
            background-color: #45a049;
        }

        #result {
            margin-top: 20px;
            font-size: 18px;
        }
    </style>
</head>
<body>
    <div class="container">
        <h1>Prime Number Checker</h1>
        <input type="number" id="input" placeholder="Enter a number">
        <button onclick="cPrime()">Check</button>
        <p id="result"></p>
    </div>
    <script>
        function cPrime() {
            const n = parseInt(document.getElementById('input').value);
            const res = document.getElementById('result');
            if (isNaN(n) || n <= 1) {
                res.textContent = "Please enter a number greater than 1.";
                res.style.color = "red";
                return;
            }
            let isPrime = true;
            for (let i = 2; i <= Math.sqrt(n); i++) {
                if (n % i === 0) {
                    isPrime = false;
                    break;
                }
            }
            if (isPrime) {
                res.textContent = `${n} is a Prime Number.`;
                res.style.color = "green";
            } else {
                res.textContent = `${n} is a Non-Prime Number.`;
                res.style.color = "blue";
            }
        }
    </script>
</body>
</html>

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Article Tags :

JavaScript Application To Check Prime and Non-Prime Number

What We Are Going to Create

Project Preview

Prime and Non-Prime Number - HTML & CSS Structure

Prime and Non-Prime Number - JavaScript Functionality

Complete Code

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