/** * Binary search is an efficient algorithm for finding an item from a sorted list of items. * It works by repeatedly dividing in half the portion of the list that could contain the item, * until you've narrowed down the possible locations to just one. */ function binarySearch(arr, x, left, right) { if (left > right) { return false; } const middle = Math.floor(left + (right - left) / 2); if (arr[middle] === x) { return true; } else if (x < arr[middle]) { return binarySearch(arr, x, left, middle - 1); } else { return binarySearch(arr, x, middle + 1, right); } } export default function (arr, x) { return binarySearch(arr, x, 0, arr.length); }