Introduction to Bubble Sort in JavaScript
It is the sorting algorithm that performs by repeated sorts of an array element by comparing the adjacent elements. It compares the adjacent element and it swaps the element if they are in the wrong order. This algorithm runs repeatedly until all the elements in the lists are sorted. If all the elements sorted in the list, then the algorithms end automatically. Although the bubble sort algorithm is simple, it consumes more time comparing other sorting techniques. IKn this topic, we are going to learn about Bubble Sort in JavaScript
Workflow with an Example
We have ten numbers in an array. In this case, we need to compare nine numbers, so that the largest number will be sorted to the top of the array. The reason for comparing 9 numbers instead of 10 because
n = number of elements present in the array
n – 1 = Number of times the comparison occurs
Therefore: 10 – 1 = 9.
Step 1: Compare the first two numbers ‘2’ and ‘7’.
No swap, because ‘2’ is smaller than ‘7’.
2 7 4 1 10 8 3 5 6 9
Step 2: Compare second and third numbers ‘7’ and ‘4’.
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2 4 7 1 10 8 3 5 6 9
Swap, because ‘7’ is larger than ‘4’.
Step 3: Compare third and fourth numbers ‘7’ and ‘1’.
2 4 1 7 10 8 3 5 6 9
Numbers have been swapped
Step 4: Compare fourth and fifth numbers ‘7’ and ’10’.
2 4 1 7 10 8 3 5 6 9
No swap, because they are in order.
Step 5: Compare fifth and sixth numbers ’10’ and ‘8’.
2 4 1 7 8 10 3 5 6 9
They had to swap.
Step 6: Compare sixth and seventh numbers ’10’ and ‘3’.
2 4 1 7 8 3 10 5 6 9
They had to swap.
Step 7: Compare seventh and eighth numbers ’10’ and ‘5’.
2 4 1 7 8 3 5 10 6 9
They had to swap.
Step 8: Compare eighth and ninth numbers ’10’ and ‘6’.
2 4 1 7 8 3 5 6 10 9
They had to swap.
Step 9: Compare ninth and tenth numbers ’10’ and ‘9’.
2 4 1 7 8 3 5 6 9 10
They had to swap. So, as you can see from above sort ’10’, the largest number has “bubbled” to the end of the array.
Now, this step is repeated until the remaining 9 numbers are sorted in proper order as ‘1’ ‘2’ ‘3’ ‘4’ ‘5’ ‘6’ ‘7’ ‘8’ ‘9’ ’10’.
How does Bubble Sort work in JavaScript?
- In Bubble Sort, the algorithm will take the 1st element of the array and compare the value with the element next to it in the array.
- If the 1st element is larger than the 2nd, then the element will swap the positions.
- If it doesn’t satisfy the condition, then the algorithm will compare the 2nd element with 3rd
- This process continues until all the elements in the array is bubble sorted in the respective order.
Example:
Let’s take this below concept as an example and implement what we learned above.
This process will continue until the expected output comes which is 12345678.
Example for Bubble Sort in JavaScript:
<html>
<head>
<title> Bubble Sort </title>
</head>
<body>
<script>
var values=[];
var a=0,b=0;
document.write("<font face='arial' size='4'>BUBBLE SORT </font>");
document.write("<br><br>");
for (a=0; a<5; a++) {
values.push(Number(prompt("Enter item value at no. " + (a+1))));
}
document.write("<font face='arial' size='4'>Numbers");
document.write(" given by the user </font>");
document.write("<br><br>");
for (a=0;a<5; a++) {
document.write("<font face='arial' size='4'> " +values[a] + "");
}
for (a = 0; a < ( 5 - 1 ); a++) {
for (b = 0; b < 5 - a - 1; b++) {
if (values[b] > values[b+1])
{
swap= values[b];
values[b]= values[b+1];
values[b+1] = swap;
}
}
}
document.write("<br><br>");
document.write("<font face='arial' size='4'>Sorted List of Numbers </font>");
document.write("<br><br>");
for (a=0; a<5; a++) {
document.write("<font face='arial' size='4'> " + values[a]+"</font>");
}
</script>
</body>
Output:
Example 2:
When the below program is executed the Bubble Sort algorithm will sort the random bar chart which will be a different size to the order as given below in the output. i.e., smallest to largest.
//bubble sorting in JavaScript
<html>
<head>
<title>Bubble Sort</title>
<meta charset="UTF-8">
<script src=
"https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.8.0/p5.min.js"
type="text/javascript"></script>
<style>
body {
padding: 0;
}
canvas {
vertical-align: top;
}
</style>
</head>
<body>
<script type="text/javascript">
// Set Global Variables
let values = [];
let w = 20;
// To store the state of each bar
// in order to change the color
let states = [];
function setup() {
// Create Canvas of Size Windows
// Width * Windows Height
createCanvas(800, 400);
// Insert Random values in array
values = new Array(floor(width/w));
for(let i = 0; i < values.length; i++) {
values[i] = float(random(height));
states[i] = -1;
}
// Print Unsorted Array
print("Unsorted Array:" + values);
// Call to bubble sort function
bubbleSort(values, 0, values.length);
// Print Sorted Array
print("Sorted Array:" + values);
}
// Definition of bubble sort
async function bubbleSort(arr, start, end) {
if(start >= end) {
return;
}
for(var i = 0; i < end-1; i++) {
for(var j = 0; j < end-i-1; j++) {
if(arr[j] >= arr[j+1]) {
states[j] = 1;
// Call to swap function
await swap(arr, j, j+1);
states[j+1] = 0;
}
states[j] = 2;
}
}
return arr;
}
// Definition of draw function
function draw() {
background(51);
for(let i = 0; i < values.length; i++) {
stroke(0);
fill(255);
if(states[i] == 0) {
fill(255, 0, 0);
}
else if (states[i] == 1) {
// Element currently sorting
fill("#58FA82");
}
else {
fill(255);
}
rect(i*w, height - values[i], w, values[i]);
}
}
// Definition of swap function
async function swap(arr, a, b) {
await sleep(20);
let t = arr[a];
arr[a] = arr[b];
arr[b] = t;
}
// Definition of sleep function
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
</script>
</body>
</html>
Output:
Conclusion
Bubble Sort is the most inefficient algorithm. We should compare all the elements with each element in the array in the sorting algorithm. Hence, you will not be using Bubble Sort for sorting the elements in everyday code. Even though the Bubble Sort technique is the most inefficient algorithm, the programmer uses it more frequently due to its simplicity.
Recommended Articles
This is a guide to Bubble Sort in JavaScript. Here we discuss How does Bubble Sort works in JavaScript with Examples. You may also look at the following article to learn more –
