sieve.js

export default class Sieve {
  constructor(endNumber) {
    this.endNumber = endNumber;
    this.startNumber = 2;
  }

  range(start, end) {
    return Array.from({length: ((end + 1) - start)}, (v, k) => k + start);
  }

  get primes () {
    const set = new Set(this.range(this.startNumber, this.endNumber));
    const potentialNonPrimes = Array.from(set).reverse(); // We reverse to start comparing big numbers to small numbers
    set.forEach(potentialPrime => {
      //console.log(potentialPrime); // This let's you see the iterators it is checking as it goes along. 
      for (let potentialNonPrime of potentialNonPrimes) {
        if((potentialNonPrime != potentialPrime) && (potentialNonPrime % potentialPrime) === 0) {
          set.delete(potentialNonPrime);
        }
      }
    });
    return Array.from(set); // This runs in about half the time that the other solution did, 9ms instead of the 17-22ms range.
  }
}