JavaScript Number Operations Toolkit: Reverse, Factorial, Fibonacci, Armstrong & Palindrome

Here’s a JavaScript code that combines several functionalities, including reversing a number, finding the factorial, generating the Fibonacci series, checking for Armstrong numbers, and checking for palindromes. This will provide an interactive menu where the user can choose which operation to perform.

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Number Operations</title>
    <script>
        // Function to reverse a number
        function reverseNumber(num) {
            return num.toString().split('').reverse().join('');
        }

        // Function to calculate factorial of a number
        function factorial(num) {
            if (num === 0 || num === 1) return 1;
            let result = 1;
            for (let i = 2; i <= num; i++) {
                result *= i;
            }
            return result;
        }

        // Function to generate Fibonacci series up to n terms
        function fibonacci(n) {
            let fibSeries = [0, 1];
            for (let i = 2; i < n; i++) {
                fibSeries.push(fibSeries[i - 1] + fibSeries[i - 2]);
            }
            return fibSeries;
        }

        // Function to check if a number is an Armstrong number
        function isArmstrong(num) {
            let sum = 0;
            let temp = num;
            const length = num.toString().length;
            while (temp > 0) {
                let digit = temp % 10;
                sum += Math.pow(digit, length);
                temp = Math.floor(temp / 10);
            }
            return sum === num;
        }

        // Function to check if a number is a palindrome
        function isPalindrome(num) {
            const str = num.toString();
            return str === str.split('').reverse().join('');
        }

        // Display results based on the user's choice
        function performOperation() {
            const choice = parseInt(document.getElementById("operation").value);
            const inputNumber = parseInt(document.getElementById("inputNumber").value);

            let result = '';
            switch (choice) {
                case 1:
                    result = `Reversed Number: ${reverseNumber(inputNumber)}`;
                    break;
                case 2:
                    result = `Factorial: ${factorial(inputNumber)}`;
                    break;
                case 3:
                    const fibSeries = fibonacci(inputNumber);
                    result = `Fibonacci Series (first ${inputNumber} terms): ${fibSeries.join(', ')}`;
                    break;
                case 4:
                    result = isArmstrong(inputNumber) ? `${inputNumber} is an Armstrong number` : `${inputNumber} is NOT an Armstrong number`;
                    break;
                case 5:
                    result = isPalindrome(inputNumber) ? `${inputNumber} is a Palindrome` : `${inputNumber} is NOT a Palindrome`;
                    break;
                default:
                    result = "Invalid choice! Please select a valid operation.";
                    break;
            }

            document.getElementById("result").innerText = result;
        }
    </script>
</head>
<body>
    <h2>Number Operations</h2>
    <label for="inputNumber">Enter a number:</label>
    <input type="number" id="inputNumber" placeholder="Enter number" required><br><br>

    <label for="operation">Select an operation:</label>
    <select id="operation">
        <option value="1">Reverse Number</option>
        <option value="2">Factorial</option>
        <option value="3">Fibonacci Series</option>
        <option value="4">Armstrong Number</option>
        <option value="5">Palindrome Check</option>
    </select><br><br>

    <button onclick="performOperation()">Perform Operation</button>

    <h3>Result:</h3>
    <p id="result"></p>
</body>
</html>

Explanation

Reverse Number: The function reverseNumber takes the input number, converts it to a string, splits it into an array, reverses it, and joins it back together to produce the reversed number.
Factorial: The factorial function calculates the factorial of a number by multiplying all integers from 1 to the given number.
Fibonacci Series: The fibonacci function generates the Fibonacci series up to n terms, where n is the number entered by the user.
Armstrong Number: The isArmstrong function checks if the entered number is an Armstrong number. An Armstrong number is a number that is equal to the sum of its own digits each raised to the power of the number of digits.
Palindrome: The isPalindrome function checks if the entered number reads the same backward as forward.

How it works

The user enters a number and selects an operation from the dropdown.
When the user clicks the "Perform Operation" button, the corresponding function is called, and the result is displayed below the button.