30-seconds-of-code/snippets/generateUntil.md

title, tags, firstSeen

title	tags	firstSeen
generateUntil	function,generator,advanced	2022-01-21T05:00:00-04:00

Creates a generator, that keeps producing new values until the given condition is met.

• Initialize the current val using the seed value.
• Use a while loop to iterate while the condition function called with the current val returns false.
• Use yield to return the current val and optionally receive a new seed value, nextSeed.
• Use the next function to calculate the next value from the current val and the nextSeed.

const generateUntil = function* (seed, condition, next) {
  let val = seed;
  let nextSeed = null;
  while (!condition(val)) {
    nextSeed = yield val;
    val = next(val, nextSeed);
  }
  return val;
};

[...generateUntil(1, v => v > 5, v => ++v)]; // [1, 2, 3, 4, 5]