Check sum of ordered array with JavaScript

checkSum.js

function checkSum(arr, sum) {
	let low = 0,
	  high = arr.length - 1;

	while(low < high) {
	  let s = arr[low] + arr[high];

		if (s === sum) return true
		if (s < sum) {
			low = low + 1
		}
		if (s > sum) {
			high = high - 1
		}
	}

	return false
}