Generate prime numbers

sieve-of-eratosthenes.js

/**
 * Generate Set of prime numbers up to `maxPrime`
 * https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
 * 
 * @param {Number} maxPrime
 * @returns {Set}
 */
function getPrimes (maxPrime) {
  const sieve = new Map
  const result = new Set
  let currNum, i

  // initially make all numbers possibly prime
  for (i = 2; i <= maxPrime; i++) sieve.set(i, 1)

  for (currNum = 2; currNum <= maxPrime; currNum++) {
    if (sieve.get(currNum) === 1) {
      result.add(currNum)

      // mark all multiples as non-prime
      for (i = currNum * 2; i <= maxPrime; i += currNum) {
        sieve.set(i, 0)
      }
    }
  }

  return result
}