findArmstrongNumbersRange()

Step 1: Understanding Armstrong Numbers

Before we dive into the code, it's crucial to understand what an Armstrong number is. A number is defined as an Armstrong number if the sum of its own digits each raised to the power of the number of digits is equal to the number itself. For example, 153 is an Armstrong number because it has 3 digits, and 1^3 + 5^3 + 3^3 = 153.

// For understanding, let's manually check if 153 is an Armstrong number
let number = 153; // Number to check
let numberOfDigits = number.toString().length; // Get number of digits
let sum = 0; // Initialize sum

for(let digit of number.toString()) {  // Convert number to string to loop through each digit
    sum += Math.pow(parseInt(digit), numberOfDigits); // Add the digit raised to the power of number of digits to the sum
}

console.log(sum === number); // Check if the sum is equal to the number

Step 2: Creating a function to check Armstrong number

From step 1, the next step is to create a function that checks whether a number is an Armstrong number.

function isArmstrongNumber(number) {
    let numberOfDigits = number.toString().length;
    let sum = 0;

    for(let digit of number.toString()) {
        sum += Math.pow(parseInt(digit), numberOfDigits);
    }

    return sum === number;
}

console.log(isArmstrongNumber(153)); // need to return true, as 153 is an Armstrong number

Step 3: Creating a function for a range of numbers

Thereafter, we need to create a function, findArmstrongNumbersRange, that finds all the Armstrong numbers in a given range. This function should loop through each number in the range and call our isArmstrongNumber function to check if it's an Armstrong number.

function findArmstrongNumbersRange(start, end) {
    let armstrongNumbers = []; // Empty array to hold Armstrong numbers

    for(let i = start; i <= end; i++) { 
        if(isArmstrongNumber(i)) { 
            armstrongNumbers.push(i); // Push number into array if it's an Armstrong number
        }
    }

    return armstrongNumbers;
}

console.log(findArmstrongNumbersRange(100, 999)); // returns [153, 370, 371, 407]

Step 4: Optimizing the function

You can optimize the function by not checking the numbers with only one digit because all single digit numbers are Armstrong numbers.

function findArmstrongNumbersRange(start, end) {
    let armstrongNumbers = [];

    start = Math.max(start, 10); // If start is less than 10, start from 10
    for(let i = start; i <= end; i++) {
        if(isArmstrongNumber(i)) {
            armstrongNumbers.push(i);
        }
    }

    return armstrongNumbers;
}

The final code is an efficient solution for finding all the Armstrong numbers in a given range.

Conclusion

In this post, we've gone through a step-by-step demonstration of how to come up with a function, findArmstrongNumbersRange that finds all Armstrong numbers between two given numbers. This involved understanding what Armstrong numbers are, creating a helper function to check if a number is an Armstrong number, and finally creating our main function. We also managed to optimize our function for better performance. Armed with these insights, you can now handle tasks involving Armstrong numbers with more proficiency.