Heap Sort Visualization using JavaScript

Last Updated : 30 May, 2023

GUI(Graphical User Interface) helps in better understanding than programs. In this article, we will visualize Heap Sort using JavaScript. We will see how the array is first converted into Maxheap and then how we get the final sorted array. We will also visualize the time complexity of Heap Sort.

Refer:

Approach:

First, we will generate a random array using Math.random() function.
Different colors are used to indicate which elements are being compared, sorted, and unsorted.
Since the algorithm performs the operation very fast, the setTimeout() function has been used to slow down the process.
New array can be generated by pressing the “Ctrl+R” key.
The sorting is performed using HeapSort() function using Heapify() function.

Example: In this example, we will see the visualization of Heap Sort by using the above approach.

Below is the program to visualize the Heap Sort algorithm.

index.html

HTML

<!DOCTYPE html>
<html lang="en">

<head>
    <link rel="stylesheet" 
          href="style.css" />
</head>

<body>
    <br />
    <p class="header">Heap Sort</p>
    <div id="array"></div>
    <div id="count"></div>
    <script src="script.js"></script>
</body>

</html>

style.css: The following is the content for “style.css” used in the above file.

CSS

* {
    margin: 0px;
    padding: 0px;
    box-sizing: border-box;
}
.header {
    font-size: 20px;
    text-align: center;
}
#array {
    background-color: white;
    height: 270px;
    width: 598px;
    margin: auto;
    position: relative;
    margin-top: 64px;
}
.block {
    width: 28px;
    background-color: #6b5b95;
    position: absolute;
    bottom: 0px;
    transition: 0.2s all ease;
}
.block_id {
    position: absolute;
    color: black;
    margin-top: -20px;
    width: 100%;
    text-align: center;
}
.block_id2 {
    position: absolute;
    color: black;
    margin-top: 22px;
    width: 100%;
    text-align: center;
}
.block2 {
    width: 28px;
    background-color: darkgray;
    position: absolute;
    transition: 0.2s all ease;
}
.block_id3 {
    position: absolute;
    color: black;
    margin-top: 1px;
    width: 100%;
    text-align: center;
}
#count {
    height: 20px;
    width: 598px;
    margin: auto;
}

script.js: The following is the content for “script.js” file used in the above HTML code.

JavaScript

let container = document.getElementById("array");

// Function to generate the array of blocks
function generatearray() {
    for (let i = 0; i < 20; i++) {

        // Return a value from 1 to 100 (both inclusive)
        let value = Math.ceil(Math.random() * 100);

        // Creating element div
        let array_ele = document.createElement("div");

        // Adding class 'block' to div
        array_ele.classList.add("block");

        // Adding style to div
        array_ele.style.height = `${value * 3}px`;
        array_ele.style.transform = `translate(${i * 30}px)`;

        // Creating label element for displaying
        // size of particular block
        let array_ele_label = document.createElement("label");
        array_ele_label.classList.add("block_id");
        array_ele_label.innerText = value;

        // Appending created elements to index.html
        array_ele.appendChild(array_ele_label);
        container.appendChild(array_ele);
    }
}

// Function to generate the indexes
let count_container = document.getElementById("count");
function generate_idx() {
    for (let i = 0; i < 20; i++) {

        // Creating element div
        let array_ele2 = document.createElement("div");

        // Adding class 'block2' to div
        array_ele2.classList.add("block2");

        // Adding style to div
        array_ele2.style.height = `${20}px`;
        array_ele2.style.transform = `translate(${i * 30}px)`;

        // Giving indexes
        let array_ele_label2 = document.createElement("label");
        array_ele_label2.classList.add("block_id3");
        array_ele_label2.innerText = i;

        // Appending created elements to index.html
        array_ele2.appendChild(array_ele_label2);
        count_container.appendChild(array_ele2);
    }
}

// Asynchronous Heapify function
async function Heapify(n, i) {
    let blocks = document.querySelectorAll(".block");
    let largest = i; // Initialize largest as root
    let l = 2 * i + 1; // left = 2*i + 1
    let r = 2 * i + 2; // right = 2*i + 2

    // If left child is larger than root
    if (
        l < n &&
        Number(blocks[l].childNodes[0].innerHTML) >
        Number(blocks[largest].childNodes[0].innerHTML)
    )
        largest = l;

    // If right child is larger than largest so far
    if (
        r < n &&
        Number(blocks[r].childNodes[0].innerHTML) >
        Number(blocks[largest].childNodes[0].innerHTML)
    )
        largest = r;

    // If largest is not root
    if (largest != i) {
        let temp1 = blocks[i].style.height;
        let temp2 = blocks[i].childNodes[0].innerText;
        blocks[i].style.height = blocks[largest].style.height;
        blocks[largest].style.height = temp1;
        blocks[i].childNodes[0].innerText =
            blocks[largest].childNodes[0].innerText;
        blocks[largest].childNodes[0].innerText = temp2;

        await new Promise((resolve) =>
            setTimeout(() => {
                resolve();
            }, 250)
        );

        // Recursively Hapify the affected sub-tree
        await Heapify(n, largest);
    }
}

// Asynchronous HeapSort function
async function HeapSort(n) {
    let blocks = document.querySelectorAll(".block");

    // Build heap (rearrange array)
    for (let i = n / 2 - 1; i >= 0; i--) {
        await Heapify(n, i);
    }

    // One by one extract an element from heap
    for (let i = n - 1; i > 0; i--) {

        // Move current root to end
        let temp1 = blocks[i].style.height;
        let temp2 = blocks[i].childNodes[0].innerText;
        blocks[i].style.height = blocks[0].style.height;
        blocks[0].style.height = temp1;
        blocks[i].childNodes[0].innerText =
            blocks[0].childNodes[0].innerText;
        blocks[0].childNodes[0].innerText = temp2;

        await new Promise((resolve) =>
            setTimeout(() => {
                resolve();
            }, 250)
        );

        // Call max Heapify on the reduced heap
        await Heapify(i, 0);
    }
}
// Calling generatearray function
generatearray();
// Calling generate_idx function
generate_idx();
// Calling HeapSort function
HeapSort(20);