formatSeconds

  1. const formatSeconds = s => {
  2.   const [hour, minute, second, sign] =
  3.     s > 0
  4.       ? [s / 3600, (s / 60) % 60, s % 60, '']
  5.       : [-s / 3600, (-s / 60) % 60, -s % 60, '-'];
  7.   return (
  8.     sign +
  9.     [hour, minute, second]
  10.       .map(v => `${Math.floor(v)}`.padStart(2, '0'))
  11.       .join(':')
  12.   );
  13. };
  15. formatSeconds(200); // '00:03:20'
  16. formatSeconds(-200); // '-00:03:20'
  17. formatSeconds(99999); // '27:46:39'

rangeGenerator

  1. const rangeGenerator = (end, start = 0, step = 1) => {
  2.   function* generateRange() {
  3.     let x = start - step;
  4.     while(x < end - step) yield x += step;
  5.   }
  6.   return {
  7.     [Symbol.iterator]: generateRange
  8.   };
  9. }
  11. console.log([...rangeGenerator(7)]); // [0, 1, 2, 3, 4, 5, 6]
  12. for (let i of rangeGenerator(8, 2, 2)) console.log(i); // Logs: 2, 4, 6

dateRangeGenerator

  1. const dateRangeGenerator = function* (start, end, step = 1) {
  2.   let d = start;
  3.   while (d < end) {
  4.     yield new Date(d);
  5.     d.setDate(d.getDate() + step);
  6.   }
  7. };
  8. [...dateRangeGenerator(new Date('2021-06-01'), new Date('2021-06-04'))];
  9. // [ 2021-06-01, 2021-06-02, 2021-06-03 ]