Loops in JavaScript for, while & do...while Explained with Examples- Quipoin

Loop in javaScript-tutorial

In JavaScript, loops let us execute a block of code multiple times perfect for tasks like printing numbers, iterating through arrays, or repeating actions until a condition changes.

There are three main types of loops in JavaScript

for loop

while loop

do while loop

for loop

Use a for loop when you know in advance how many times you want to repeat a block of code.

Syntax:

for (initialization; condition; update) {
   // Code to execute
}

Example:

<!DOCTYPE html>
<html>

<body>
    <script>
        for (var i = 1; i <= 5; i++) {
            document.write(i + "<br/>");
        }
    </script>
</body>

</html>

Output

While loop

Use a while loop when you do not know exactly how many times you need to loop the loop continues a s long as the condition is true.

Syntax:

while (condition) {
   // Code to execute
}

Example:

<!DOCTYPE html>
<html>

<body>
    <script>
        var i = 12;
        while (i <= 14) {
            document.write(i + "<br/>");
            i++;
        }
    </script>
</body>

</html>

Output

do While loop

A do while loop is similar to a while loop, but is always executes the block of code at least once, even if the condition is false initially.

Syntax:

do {
   // Code to execute
} while (condition);

Example:

<!DOCTYPE html>
<html>

<body>
    <script>
        var i = 21;
        do {
            document.write(i + "<br/>");
            i++;
        } while (i <= 25);
    </script>
</body>

</html>

Output

Key Point

Use for when you know the count.

Use while when the number of loops depends on a condition.

Use do while to run at least once, even if the condition is false.