Drop list elements from the right based on function

OSCC · JavaScript, Array · Oct 19, 2020

Removes elements from the end of an array until the passed function returns true. Returns the remaining elements in the array.

  • Loop through the array, using Array.prototype.slice() to drop the last element of the array until the value returned from func is true.
  • Return the remaining elements.
const dropRightWhile = (arr, func) => {
  let rightIndex = arr.length;
  while (rightIndex-- && !func(arr[rightIndex]));
  return arr.slice(0, rightIndex + 1);
};
dropRightWhile([1, 2, 3, 4], n => n < 3); // [1, 2]

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