The basic difference between while and do-while loop is that, in while loop the condition is checked before execution of block, but in do-while the condition is checked after executing the block. Because of this, the code inside the loop is executed at least one in a do-while loop.

In this tutorial, we will learn how to define/write a JavaScript Do-While loop, and its usage using example programs.

Syntax

The syntax of JavaScript Do-While Loop is


do {
     //statements
 } while (condition);

where condition is the expression which is checked after executing the statements inside the loop.

do and while are keywords.

Examples

In the following example, we execute a block of code that appends ‘hello world’ to a pre block HTML element ten times using a Do-While Loop.


<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var i = 0;
        do {
            document.getElementById('output').innerHTML += 'hello world\n';
            i++;
        } while (i < 10);
    </script>
</body>
</html>

Output:

Even if the condition is false for the first time, the code inside loop will be executed at least once.

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JavaScript Do-While Loop