Heap sort algorithm based on JavaScript.

heapSort.js

function heapSort(arr) {
  for (let i = (arr.length >> 1) - 1; i >= 0; i--) {
    adjust(arr, i, arr.length);
  }

  for (let j = arr.length - 1; j >= 0; j--) {
    swap(arr, 0, j);
    adjust(arr, 0, j);
  }

  return arr;
}

function adjust(arr, index, length) {
  let currIndex = index;

  for (let i = (index << 1) + 1; i < length; i++) {
    if (i + 1 < length && arr[i + 1] > arr[i]) {
      i++;
    }

    if (arr[i] > arr[currIndex]) {
      swap(arr, i, currIndex);
      currIndex = i;
    } else {
      break;
    }
  }
}

function swap(arr, a, b) {
  const temp = arr[a];
  arr[a] = arr[b];
  arr[b] = temp;
}