Binary Search (recursive or iterative implementations)

binary-search-iterative.js

function bsr(arr, m) {
  let l = 0;
  let r = arr.length - 1;

  while (l <= r) {
    const mid = (l + (r - l) / 2) | 0;
    const val = arr[mid];

    if (val === m) return mid;
    if (m > val) l = mid + 1;
    if (m < val) r = mid - 1;
  }

  return -1;
}

a = [1, 2, 3, 4, 5, 6, 7, 8, 10, 12];
b = 3;

bsr(a, b);

binary-search-recursive.js

function bsr(arr, l, r, m) {
  const mid = (l + (r  - l) / 2) | 0;
  const val = arr[mid];

  // Ensure `l` is always less than or equal to `r`.
  // When `m` is not inside `arr`, `l` will exceed `r`
  // which is the the last index of `arr` as we are
  // always adding 1 to `l` when `m > val` fulfills.
  if (l <= r) {
    if (val === m) return mid;
    if (m > val) return bs(arr, mid + 1, r, m);
    if (m < val) return bs(arr, l, mid - 1, m);
  }

  return -1;
}

a = [1, 2, 3, 4, 5, 6, 7, 8, 10, 12];
b = 3;
c = bsr(a, 0, a.length - 1, b);

c;