freeCodeCamp Challenge Guide: Sum multiples of 3 and 5

Guide
1

Sum multiples of 3 and 5

Solutions

Solution 1 (Click to Show/Hide) 
function sumMults(n) {
  var sum = 0;
  for (var i = 1; i < n; i++) {
    if (i % 3 == 0 || i % 5 == 0) sum += i;
  }
  return sum;
}