Implementing Heap Sort Using Vanilla JavaScript

Heap Sort is basically a comparison-based sorting algorithm. It can be thought of as an improved selection sort − like that algorithm, it divides its input into a sorted and an unsorted region, and it interactively shrinks the unsorted region by extracting the target (largest or smallest) element and moving that to the sorted region.

Example

The code for this will be −

const constructHeap = (arr, ind) => {
   let left = 2 * ind + 1;
   let right = 2 * ind + 2;
   let max = ind;
   if (left < len && arr[left] > arr[max]) {
      max = left;
   }
   if (right < len && arr[right] > arr[max]) {
      max = right;
   }
   if (max != ind) {
      swap(arr, ind, max);
      constructHeap(arr, max);
   }
}
function swap(arr, index_A, index_B) {
   let temp = arr[index_A];
   arr[index_A] = arr[index_B];
   arr[index_B] = temp;
}
function heapSort(arr) {
   len = arr.length;
   for (let ind = Math.floor(len / 2); ind >= 0; ind −= 1) {
      constructHeap(arr, ind);
   }
   for (ind = arr.length − 1; ind > 0; ind−−) {
      swap(arr, 0, ind);
      len−−;
      constructHeap(arr, 0);
   }
}
const arr = [3, 0, 2, 5, −1, 4, 1];
heapSort(arr);
console.log(arr);
var len;

Output

And the output in the console will be −

[
   −1, 0, 1, 2,
   3, 4, 5
]