JavaScript While Loop

JavaScript While Loop is used to execute a block of code for a number of times based on a condition.

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

Syntax

The syntax of JavaScript While Loop is

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 while (condition) {
     //statements
 }

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

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 While Loop.

index.html

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

We can also use a while to iterate over the elements of an array, using array length in condition, as shown in the following example.

index.html

<!DOCTYPE html>
<html lang="en">
<body>
    <pre id="output"></pre>
    <script>
        var arr = [10, 20, 30, 40];
        var i = 0;
        while (i < arr.length) {
            document.getElementById('output').innerHTML += arr[i] + '\n';
            i++;
        }
    </script>
</body>
</html>

Conclusion

In this JavaScript Tutorial, we learned about While Loop, its syntax, and usage with examples.

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JavaScript While Loop