Remove list elements from the end while condition is met

OSCC · JavaScript, Array · Nov 29, 2020

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]

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