# Implementing Heap Sort using vanilla JavaScript

JavascriptWeb DevelopmentFront End TechnologyObject Oriented Programming

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
]