findHarshadNumbersRange()

Step 1: Understand the Problem

The task is to write a function named findHarshadNumbersRange that takes two integer parameters, a start number and an end number, and returns an array of all Harshad (or Niven) numbers in this range, inclusive. A Harshad or Niven number is an integer that is divisible by the sum of its digits.

We need to implement the function using JavaScript.

function findHarshadNumbersRange(start, end) {
    // Our code will go here
}

Step 2: Initialize an Empty Array to Store Harshad Numbers

To store the harshad numbers we find in the defined range, we need to create an empty array.

function findHarshadNumbersRange(start, end) {
    let harshadNumbers = [];
    // Our code will go here
}

Step 3: Loop Through the Range

To find the Harshad numbers in the provided range, we need to create a loop that starts from the "start" value and iterates up to including the "end" value.

function findHarshadNumbersRange(start, end) {
    let harshadNumbers = [];
    for (let i=start; i<=end; i++) {
        // Our code will go here
    }
}

Step 4: Calculate the Sum of Digits

During the loop process, we need to find the sum of digits of each number. We can find the digits of a number by first transforming it into a string (using the .toString() method), then splitting the string into an array of characters (using the .split('') method), and then converting those string characters back to numbers before summing them up.

function findHarshadNumbersRange(start, end) {
    let harshadNumbers = [];
    for (let i=start; i<=end; i++) {
        let digitSum = i.toString().split('').reduce((sum, num) => sum + parseInt(num, 10), 0);
        // Our code will go here
    }
}

Step 5: Check if the Number is a Harshad Number

We can check if a number is a Harshad number by dividing it by the sum of its digits and checking if the remainder is zero (i.e., the number is divisible by the sum of its digits). If it is a Harshad number, we can add it to our harshadNumbers array using the .push() method.

function findHarshadNumbersRange(start, end) {
    let harshadNumbers = [];
    for (let i=start; i<=end; i++) {
        let digitSum = i.toString().split('').reduce((sum, num) => sum + parseInt(num, 10), 0);
        if(i % digitSum === 0) harshadNumbers.push(i);
    }
    return harshadNumbers;
}

Conclusion

That's it! We have written a function in JavaScript that finds all Harshad numbers within a given range. This function iterates over each number in the provided range, calculates the sum of its digits, checks if that number is divisible by the sum of its digits, and if so, adds it to our array of Harshad numbers. Finally, it returns the array of Harshad numbers as its output.