JavaScript Program to Display Armstrong Number Between Two Intervals

An Armstrong number is a number that is equal to the sum of its digits each raised to the power of the number of digits. For example, 153 is an Armstrong number because 1^3 + 5^3 + 3^3 = 153. In this article, we'll explore how to create a JavaScript program to display all Armstrong numbers within a given range.

To find Armstrong numbers between two intervals, we need to:

• Iterate through all numbers in the given range.
• For each number, determine the number of digits (n).
• Calculate the sum of each digit raised to the power of n.
• Check if the calculated sum is equal to the original number. If it is, the number is an Armstrong number.

Basic Approach

Here's a simple implementation to find and display Armstrong numbers between two given intervals:

function isArmstrongNumber(num) {
    let sum = 0;
    let temp = num;
    const numberOfDigits = num.toString().length;

    while (temp > 0) {
        let digit = temp % 10;
        sum += Math.pow(digit, numberOfDigits);
        temp = Math.floor(temp / 10);
    }

    return sum === num;
}

function displayArmstrongNumbers(start, end) {
    for (let i = start; i <= end; i++) {
        if (isArmstrongNumber(i)) {
            console.log(i);
        }
    }
}

displayArmstrongNumbers(100, 1000);

153
370
371
407

Using Array Methods

Alternatively, you can use JavaScript array methods to make the code more concise:

function isArmstrongNumber(num) {
    return num.toString()
              .split('')
              .map(Number)
              .reduce((sum, digit, _, {length}) => sum + Math.pow(digit, length), 0) === num;
}

function displayArmstrongNumbers(start, end) {
    for (let i = start; i <= end; i++) {
        if (isArmstrongNumber(i)) {
            console.log(i);
        }
    }
}

displayArmstrongNumbers(100, 1000);

153
370
371
407

The split() method is used to convert the number to an array of digits, map(Number) converts each digit back to a number, and reduce() calculates the sum of each digit raised to the power of the number of digits.