en.javascript.info/1-js/12-generators-iterators/1-generators/01-pseudo-random-generator/solution.md

function* pseudoRandom(seed) {
  let value = seed;

  while(true) {
    value = value * 16807 % 2147483647
    yield value;
  }

};

let generator = pseudoRandom(1);

alert(generator.next().value); // 16807
alert(generator.next().value); // 282475249
alert(generator.next().value); // 1622650073

Please note, the same can be done with a regular function, like this:

function pseudoRandom(seed) {
  let value = seed;

  return function() {
    value = value * 16807 % 2147483647;
    return value;
  }
}

let generator = pseudoRandom(1);

alert(generator()); // 16807
alert(generator()); // 282475249
alert(generator()); // 1622650073

That's fine for this context. But then we loose ability to iterate with for..of and to use generator composition, that may be useful elsewhere.