JavaScript Coding Challenge: "Multiple of index"

In this article we are going to go over a coding challenge from Codewars.

Problem description

Return a new array consisting of elements which are multiple of their own index in input array (length > 1).

Some cases:

[22, -6, 32, 82, 9, 25] => [-6, 32, 25]

[68, -1, 1, -7, 10, 10] => [-1, 10]

[-56,-85,72,-26,-14,76,-27,72,35,-21,-67,87,0,21,59,27,-92,68] => [-85, 72, 0, 68]

It’s a simple problem, but we’ll spice it up by solving it using 2 different methods:

1. With a good ol’ for loop
2. With the array’s filter method

I’ll leave comments in the code to explain how it works.

The for loop solution

function multipleOfIndex(array) {
	// creating a result array where we'll save the needed elements
	let res = [];

	// loop over the array
	for (let i = 0; i < array.length; i++) {
		// check if the current element (array[i]) is a multiple of it's index (i) and if it is...
		if (array[i] % i === 0) {
			// add it to the resulting array
			res.push(array[i]);
		}
	}

	return res;
}

The array’s filter method solution

function multipleOfIndex(array) {
	// the filter method accepts the 2 arguments that we need:
	// 1. the Elements (el)
	// 2. the index (idx)
	// and returns an filtered array by removing the elements we don't need
	return array.filter((el, idx) => el % idx === 0);
}

You can read more about array’s filter method here.

Conclusion

As I said above, it is a pretty simple Coding Challenge.

Let me know if you have another way to solve it! 😄

Happy coding! 😇