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

title, tags, expertise, cover, firstSeen, lastUpdated

title	tags	expertise	cover	firstSeen	lastUpdated
Remove list elements from the end while condition is met	array	intermediate	blog_images/beach-pineapple.jpg	2018-01-26T12:55:31+02:00	2020-11-29T12:04:53+02:00

Removes elements from the end of an array until the passed function returns false. Returns the removed elements.

• Create a reversed copy of the array, using the spread operator (...) and Array.prototype.reverse().
• Loop through the reversed copy, 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 takeRightWhile = (arr, fn) => {
  for (const [i, val] of [...arr].reverse().entries())
    if (!fn(val)) return i === 0 ? [] : arr.slice(-i);
  return arr;
};

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