Binary search with typings from https://stackoverflow.com/a/50612218

binarySearch.ts

// from https://stackoverflow.com/a/50612218
export function binarySearch<X>(xs: X[], x: X) {
  let start = 0;
  let end = xs.length - 1;

  while (start <= end) {
    let mid = Math.floor((start + end) / 2);

    if (xs[mid] === x) {
      return mid;
    }

    if (x < xs[mid]) {
      end = mid - 1;
    } else {
      start = mid + 1;
    }
  }
  return -1;
}