Calculates the sum of all multiples of numbers in an array between a limit

multiples.js

/**
 * @description removes the multiples in the array
 * @param arr
 * @returns {Number}
 */
function notMultiples(arr) {
	arr = arr.sort((a, b) => a - b);
	return arr.reduce((notMul, num) => {
		if (notMul.length) {
			if ((notMul.some(div => (num % div === 0)))) {
				return notMul
			}
			notMul.push(num);
			return notMul
		}
		return [num]
	}, 0)
}

/**
 * @description finds the sum of all Numbers tll n
 * (n(n*1))/2 sum of natural Numbers till n
 * @param n the nth sum we want to get
 * @returns {Number} sum
 */
function sumOfN(n) {
	"use strict";
	return (n * (n + 1)) / 2
}

/**
 * @description finds the products of all the Numbers in the array
 * NOTE: does not include the square of the Numbers
 *
 * @param array
 * @returns {Array}
 */
function multipleAll(array) {
	let arr = [...array];
	let arrx = [];
	let x = arr.shift();
	while (arr.length) {
		let initArr = arr.map(val => x * val);
		x = arr.shift();
		arrx = arrx.concat(initArr)
	}
	return arrx
}

/**
 * @description sum of natural Numbers till n multiplied by value
 * @param val value
 * @param n the nth sum we want to get
 * @returns {Number}
 */
function sumOfNMultipliedByVal(val, n) {
	"use strict";
	return sumOfN(n) * val
}

/**
 * @description  the sum of all multiples in the array btw the num + 1
 * @param {Number} num
 * @param {Array} arr
 * @returns {Number}
 */
function sumOfAllNumbers(num, arr) {
	const dividedByN = arr.map(n => Math.floor(num / n));
	const sumOfAllNInArr = arr.map((n, i) => sumOfNMultipliedByVal(n, dividedByN[i]));
	return sumOfAllNInArr.reduce((acc, n) => acc + n,0);
}

/**
 * @description finds the sum of the multiple less than the limit
 * @param {Array} arr an array of the Number which multiple we want to get the sum
 * @param {Number} lessThan
 * @returns {Number}
 */
function sumOfMultplesOfNumbersLessThan(arr, lessThan) {
	const limit = lessThan - 1;
	const filteredMul = notMultiples(arr);
	const excessesArr = multipleAll(filteredMul);
	const sum1 = sumOfAllNumbers(limit, filteredMul);
	const sum2 = sumOfAllNumbers(limit, excessesArr);
	return sum1 - sum2;
}

module.exports = sumOfMultplesOfNumbersLessThan;

//test: find the sum of the multiples of 3 and 5 less than 1000
console.log(sumOfMultplesOfNumbersLessThan([3,5], 1000));

Calculates the sum of multiple of numbers in array less than a given number