Generate until condition is met

Angelos Chalaris · JavaScript, Function, Generator · Jan 21, 2022

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]

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