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

title, tags, expertise, author, cover, firstSeen

title	tags	expertise	author	cover	firstSeen
Generate while condition is met	function,generator	advanced	chalarangelo	blog_images/lake-loop.jpg	2022-01-21T05:00:00-04:00

Creates a generator, that keeps producing new values as long as 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 true.
• 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 generateWhile = function* (seed, condition, next) {
  let val = seed;
  let nextSeed = null;
  while (condition(val)) {
    nextSeed = yield val;
    val = next(val, nextSeed);
  }
  return val;
};

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