JavaScript while Loop

Example

Loop a code block as long as a i is less than 5:

let text = "";
let i = 0;
while (i < 5) {
text += i + " ";
i++;
}

Loop (iterate over) an array to collect car names:

const cars = ["BMW", "Volvo", "Saab", "Ford"];
let text = "";
let i = 0;
while (i < cars.length) {
text += cars[i] + " ";
i++;
}

Try it Yourself »

The loop starts in position 0 (let i = 0).
The loop increments i for each run (i++).
The loop runs as long as i < cars.length.

More examples below.

Definition and Usage

The while statement creates a loop (araund a code block) that is executed while a condition is true.

The loop runs while the condition is true. Otherwise it stops.

JavaScript Loop Statements

Statement	Description
break	Breaks out of a loop
continue	Skips a value in a loop
while	Loops a code block while a condition is true
do...while	Loops a code block once, and then while a condition is true
for	Loops a code block while a condition is true
for...of	Loops the values of any iterable
for...in	Loops the properties of an object

Syntax

while (condition) {
code block to be executed
}

Parameters

Parameter	Description
condition	Required. The condition for running the code block. If it returns true, the code clock will start over again, otherwise it ends.

Note

If the condition is always true, the loop will never end. This will crash your browser.

If you use a variable in the condition, you must initialize it before the loop, and increment it within the loop. Otherwise the loop will never end. This will also crash your browser.