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

title, tags, firstSeen, lastUpdated

title	tags	firstSeen	lastUpdated
takeWhile	array,intermediate	2018-01-26T12:55:31+02:00	2020-11-29T12:04:53+02:00

Removes elements in an array until the passed function returns false. Returns the removed elements.

• Loop through the array, using a for...of loop over Array.prototype.entries() until the returned value from the function is falsy.
• Return the removed elements, using Array.prototype.slice().
• The callback function, fn, accepts a single argument which is the value of the element.

const takeWhile = (arr, fn) => {
  for (const [i, val] of arr.entries()) if (!fn(val)) return arr.slice(0, i);
  return arr;
};

takeWhile([1, 2, 3, 4], n => n < 3); // [1, 2]