JavaScript While Loops

While loops execute a block of code as long as a specified condition is true.

JavaScript have two types of while loops:

The while loop
The do while loop

The While Loop

The while loop loops through a block of code as long as a specified condition is true.

Syntax

Example Code

javascript

Try it Yourself

while (condition) {

      // code block to be executed

}

In the following example, the code in the loop will run, over and over again, as long as a variable (i) is less than 10:

Example

Example Code

javascript

Try it Yourself

while (i   If you forget to increase the variable used in the condition, the loop will never end.
> This will crash your browser.

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## The Do While Loop

The `do while` loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

### Syntax

javascript do {

// code block to be executed

}

while (condition);

Example Code

html

Try it Yourself

> The do while runs at least once, even if the condition is false from the start.
> This is because the code block is executed before the condition is tested:

### Example

javascript do {

text += "The number is " + i;

i++;

}

while (i Do not forget to increase the variable used in the condition, otherwise > the loop will never end!

Comparing For and While

A while loop is much the same as a for loop, with statement 1 and statement 3 omitted.

Example

Example Code

javascript

Try it Yourself

const cars = ["BMW", "Volvo", "Saab", "Ford"];

let i = 0;

let text = "";

for (;cars[i];) {

    text += cars[i];

i++;

}

Example

Example Code

javascript

Try it Yourself

const cars = ["BMW", "Volvo", "Saab", "Ford"];

let i = 0;

let text = "";

 while (cars[i]) {

    text += cars[i];

i++;

}