The person in the comments said the period is only ~233k, which is correct, because you are always taking modulo 233280. But it's also easy to verify experimentally:

  let state = 6, iters = 0;
  do {
    state = (state * 9301 + 49297) % 233280;
    iters++;
  } while(state !== 6);
  console.log("period is", iters, "iters");
  //period is 233280 iters

If you instead took modulo 2^32, I believe the period would indeed be the maximal period, according to this article: https://en.wikipedia.org/wiki/Linear_congruential_generator#...