Binary Search Visualization using JavaScript

Last Updated : 22 Feb, 2022

GUI(Graphical User Interface) helps in better understanding than programs. In this article, we will visualize Binary Search using JavaScript. We will see how the elements are being traversed in Binary Search until the given element is found. We will also visualize the time complexity of Binary Search.

Reference:

Approach:

First, we will generate a random array using Math.random() function and then sort it using sort() function.
Different color is used to indicate which element is being traversed at current time.
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 searching is performed using BinarySearch() function.

Example:

Below is the program to visualize the Binary Search algorithm.

Filename: index.html

HTML

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" 
          content="width=device-width, initial-scale=1.0" />
    <link rel="stylesheet" href="style.css" />
  </head>

  <body>
    <br />
    <p class="header">Binary Search</p>




    <div id="array"></div>
    <br /><br />

    <div style="text-align: center">
      <label for="fname">
        Number to be Searched:
      </label>
      <input type="text" id="fname"
             name="fname" />
      <br /><br />
      <button id="btn" 
              onclick="BinarySearch()">Search</button>
      <br />
      <br />
      <div id="text"></div>
    </div>

    <script src="script.js"></script>
  </body>
</html>

Filename: style.css

CSS

* {
  margin: 0px;
  padding: 0px;
  box-sizing: border-box;
}

.header {
  font-size: 35px;
  text-align: center;
}

#array {
  background-color: white;
  height: 305px;
  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;
}

Filename: script.js

JavaScript

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

// Function to generate the array of blocks
function generatearray() {

  // Creating an array
  var arr = [];

  // Filling array with random values
  for (var i = 0; i < 20; i++) {
    // Return a value from 1 to 100 (both inclusive)
    var val = Number(Math.ceil(Math.random() * 100));
    arr.push(val);
  }

  // Sorting Array in ascending order
  arr.sort(function (a, b) {
    return a - b;
  });

  for (var i = 0; i < 20; i++) {
    var value = arr[i];

    // Creating element div
    var 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
    var 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);
  }
}

// Asynchronous BinarySearch function
async function BinarySearch(delay = 300) {
  var blocks = document.querySelectorAll(".block");
  var output = document.getElementById("text");

  //Extracting the value of the element to be searched
  var num = document.getElementById("fname").value;

  //Colouring all the blocks violet
  for (var i = 0; i < blocks.length; i += 1) {
    blocks[i].style.backgroundColor = "#6b5b95";
  }

  output.innerText = "";

  // BinarySearch Algorithm

  var start = 0;
  var end = 19;
  var flag = 0;
  while (start <= end) {
    //Middle index
    var mid = Math.floor((start + end) / 2);
    blocks[mid].style.backgroundColor = "#FF4949";

    //Value at mid index
    var value = Number(blocks[mid].childNodes[0].innerHTML);

    // To wait for .1 sec
    await new Promise((resolve) =>
      setTimeout(() => {
        resolve();
      }, delay)
    );

    //Current element is equal to the element
    //entered by the user
    if (value == num) {
      output.innerText = "Element Found";
      blocks[mid].style.backgroundColor = "#13CE66";
      flag = 1;
      break;
    }
    //Current element is greater than the element
    //entered by the user
    if (value > num) {
      end = mid - 1;
      blocks[mid].style.backgroundColor = "#6b5b95";
    } else {
      start = mid + 1;
      blocks[mid].style.backgroundColor = "#6b5b95";
    }
  }
  if (flag === 0) {
    output.innerText = "Element Not Found";
  }
}

// Calling generatearray function
generatearray();