// If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. // The sum of these multiples is 23. // Find the sum of all the multiples of 3 or 5 below 1000. function sumOfMultiplesLessThan(number) { "use strict"; var sum = 0, // initialize the sum locally i = 1; // starting value for iteration for (i; i < number; i += 1) { // iterate through the number if (i % 3 === 0 || i % 5 === 0) { // true if divisible by 3 or 5 sum += i; // add the iterator value i to the sum } } return sum; } console.log(sumOfMultiplesLessThan(10)); // output: 23 console.log(sumOfMultiplesLessThan(1000)); // output: 233168