30-seconds-of-code/snippets/js/s/initialize-array-until.md

title, type, language, tags, author, cover, dateModified

title	type	language	tags	author	cover	dateModified
Initialize array until	snippet	javascript	array	chalarangelo	neon-desk-2	2023-06-22T05:00:00-04:00

Initializes and fills an array with values generated by a function, until a condition is met.

• Create an empty array, arr, an index variable i and an element el.
• Use a do...while loop to add elements to the array, using the mapFn function, until the conditionFn function returns true for the given index i and element el.
• The condition function, conditionFn, takes three arguments: the current index, the previous element and the array itself.
• The mapping function, mapFn, takes three arguments: the current index, the current element and the array itself.

const initializeArrayUntil = (conditionFn, mapFn) => {
  const arr = [];
  let i = 0;
  let el = undefined;
  do {
    el = mapFn(i, el, arr);
    arr.push(el);
    i++;
  } while (!conditionFn(i, el, arr));
  return arr;
};

initializeArrayUntil(
  (i, val) => val > 10,
  (i, val, arr) => (i <= 1 ? 1 : val + arr[i - 2])
); // [1, 1, 2, 3, 5, 8, 13]