eratosthing-lists.js

'use strict';

function putComposite(composites, value, delta) {
  let next = value + delta;
  let deltas = composites[next] || (composites[next] = []);
  deltas.push(delta);
}

function scanComposites(composites, value) {
  if (!composites[value]) {
    return false;
  }
  let deltas = composites[value];
  for (let i = 0; i < deltas.length; i++) {
    putComposite(composites, value, deltas[i]);
  }
  delete composites[value];
  return true;
}

module.exports = function*() {
  let composites = {};
  yield 2;
  for (let value = 3; true; value += 2) {
    if (!scanComposites(composites, value)) {
      yield value;
      putComposite(composites, value, value * 2);
    }
  }
};