Binary Search

function binarySearch(arr, target, left, right) {
  if (left > right) {
    return -1; // Not found
  }
  
  let mid = Math.floor((left + right) / 2);
  
  if (arr[mid] === target) {
    return mid; // Found!
  } 
  else if (arr[mid] > target) {
    // Divide: Discard right half
    return binarySearch(arr, target, left, mid - 1);
  } 
  else {
    // Divide: Discard left half
    return binarySearch(arr, target, mid + 1, right);
  }
}