Lesson 10 - Do-While Loop in JavaScript

A do-while loop is similar to the while loop, but it executes the instructions once before checking for the condition it's supposed to obey. So, it's like I say "keep learning while I am arround". Then you start learn, and then you realize I was not around. But, as far as, I am, you will continue learning.

So lte's see how to implement the do-whille in Javascript.

let number = 0;

do {
  console.log("Number is: " + number);
  number++;
} while (number < 5);

Explanation:

A do-while loop is similar to a while loop but guarantees at least one execution before checking the condition.
The loop runs the block of code once, then checksif number < 5 to determine whether to continue.
This is useful when you need to execute something at least once, regardless of the condition.

A great example of third point is when we need to show an application menu and give the user the opportunity to select what to do.

const option = 3;
do {
console.log('SELECT OPTION:');
console.log(" 0 - Menu ");
console.log(" 1 - Orders ");
console.log(" 2 - Products ");
console.log(" 3 - Exit ");

//...
}while(option != 3);

Try your hand:

1. Create a File

Create a new file namedlesson10-do-while-loop.html.

2. Write the Code

Copy and paste the following code into your file:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Day 10 - Do-While Loop</title>
</head>
<body>
    <script>
        let number = 0;

        do {
            console.log("Number is: " + number);
            number++;
        } while (number < 5);
    </script>
</body>
</html>

Save the file in your folder.

3. Preview the File:

Open the file in your browser and access the developer console.
Observe the output:

Number is: 0
Number is: 1
Number is: 2
Number is: 3
Number is: 4

4. Experiment:

Changenumber = 10 and refresh the browser.
What happens? The loop still runs once before checking while (number < 5), proving the do-while behavior.
Change the condition from number < 5 to number < 10 and observe how the loop behaves.

Javascript in 100 bits

Course by zooboole,

Last Updated on 2025-01-28 08:04:00