three-and-five.js

// Adds all the natural numbers below `end` that are multiples of any of the
// values in `multiples`
//
// end - The Number that is the upper limit
// multiples - An Array of Numbers that will be checked for divisibility
//
// Examples
//
//   multiples(1000, [3, 5])
//   // => 233168
//
// Returns the Number sum of the multiples (see description)
function multiples(end, multiples) {

  // create an array of number starting at 0 and ending at `end`
  var range = _.range(end);

  // filter the array to only contain numbers that are multiples of the numbers in `multiples`
  var filtered = _.filter(range, function(i) {
    // return true if i is divisible by any of the numbers in multiples
    return _.any(multiples, function(mult) {
      // return true if i is divisible by `mult`
      return i % mult === 0;
    });
  });

  // sum the numbers and return the result
  return _.reduce(filtered, function(a, b) {
    return a + b;
  });
}

console.assert( multiples(1000, [3, 5]) === 233168 );
console.log("multiples: Success");