Get all factors of a number

get-factors.js

/**
 * Get all factors of a number
 * 
 * @param {Number} num
 * @returns {Set}
 */
function getFactors (num) {
  const numRoot = Math.sqrt(num)
  const isEven = num % 2 === 0
  const incr = isEven ? 1 : 2
  const result = new Set([1, num])

  for (let factor = isEven ? 2 : 3; factor <= numRoot; factor += incr) {
    if (num % factor === 0) {
      const compliment = num / factor

      result.add(factor)
      if (compliment !== factor) {
        result.add(compliment)
      }
    }
  }

  return result
}