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

takeWhile

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

Loop through the array, using a for...of loop over Array.keys() until the returned value from the function is true. Return the removed elements, using Array.slice().

const takeWhile = (arr, func) => {
  for(let i of arr.keys())
    if (func(arr[i])) return arr.slice(0,i);
  return arr;
};

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