JavaScript Loops

JavaScript while Loop

Written by Swapnil RajaPublished 30 Jul 2026

The JavaScript while loop is used to repeat a block of code as long as a condition is true.

It is useful when you do not know exactly how many times the loop should run.

Example

javascript

let i = 1;

while (i <= 5) {
  console.log(i);
  i++;
}

In this example, the loop runs while i is less than or equal to 5.

What is a while Loop?

A while loop checks a condition before running the code block.

If the condition is true, the code inside the loop runs.

If the condition is false, the loop stops.

Syntax

javascript

while (condition) {
  // code to repeat
}

The condition is written inside parentheses ().

The code to repeat is written inside curly braces {}.

Simple while Loop Example

javascript

let count = 1;

while (count <= 3) {
  console.log("Hello JavaScript");
  count++;
}

Here, the message runs three times.

The value of count increases after every loop run.

Understanding How while Loop Works

Example

Understanding How while Loop Works

javascript

let number = 1;

while (number <= 5) {
  console.log(number);
  number++;
}

Step by step:

Step	Value of number	Condition	Result
1	1	`1 <= 5`	Runs
2	2	`2 <= 5`	Runs
3	3	`3 <= 5`	Runs
4	4	`4 <= 5`	Runs
5	5	`5 <= 5`	Runs
6	6	`6 <= 5`	Stops

Counting Numbers with while Loop

You can use a while loop to count numbers.

Example

Counting Numbers with while Loop

javascript

let i = 1;

while (i <= 10) {
  console.log(i);
  i++;
}

This prints numbers from 1 to 10.

Counting Backward

You can also count backward using a while loop.

Example

Counting Backward

javascript

let i = 5;

while (i >= 1) {
  console.log(i);
  i--;
}

This prints numbers from 5 to 1.

while Loop with Arrays

A while loop can be used to read array values.

Example

while Loop with Arrays

javascript

let fruits = ["Apple", "Banana", "Mango"];
let i = 0;

while (i < fruits.length) {
  console.log(fruits[i]);
  i++;
}

Here, the loop runs until all array items are printed.

while Loop with Strings

You can also use a while loop to read characters from a string.

Example

while Loop with Strings

javascript

let name = "John";
let i = 0;

while (i < name.length) {
  console.log(name[i]);
  i++;
}

This prints each character of "John" one by one.

Updating the Loop Variable

In a while loop, you must update the loop variable manually.

Example

Updating the Loop Variable

javascript

let i = 1;

while (i <= 5) {
  console.log(i);
  i++;
}

Here, i++ is important.

It increases the value of i after every loop run.

Without this update, the loop may never stop.

Complete Example

html

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript while Loop</title>
</head>
<body>

  <h1>JavaScript while Loop</h1>

  <p id="result"></p>

  <script>
    let i = 1;
    let result = "";

    while (i <= 5) {
      result += "Number: " + i + "<br>";
      i++;
    }

    document.getElementById("result").innerHTML = result;
  </script>

</body>
</html>

Try It Yourself

Run the above example in the Try It Editor.

Try changing the condition.

Example

Try It Yourself

javascript

while (i <= 10) {
  result += "Number: " + i + "<br>";
  i++;
}

Also try counting backward from 5 to 1.

Important Points

The while loop repeats code while a condition is true.
The condition is checked before the code block runs.
If the condition is false at the beginning, the loop does not run.
You must update the loop variable manually.
Without a proper update, a while loop can run forever.
A while loop is useful when you do not know the exact number of repetitions in advance.

Conclusion

The JavaScript while loop is used to repeat code as long as a condition remains true.

It is useful when the number of repetitions depends on a condition.

Understanding the while loop helps you handle repeated tasks, dynamic checks, arrays, strings, and many real-world JavaScript problems.

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