JavaScript whileStatement

Example

The loop in this example will continue to run as long as the variable i is less than 5:

var text = "";
var i = 0;
while (i < 5) {
text += " The number is " + i;
i++;
}

textOutput:

The number is 0
The number is 1
The number is 2
The number is 3
The number is 4

More examples are included at the bottom of this article.

The while statement executes a loop as long as a specified condition is true.

As long as the specified condition is true, the loop can continue to execute code.

JavaScript supports different types of loops:

for - Loop a block of code a certain number of times
for/in - Loop through the properties of an object
while - Loop through a specified block of code when a specified condition is true
do/while- Also loops through a specified block of code when a specified condition is true, but this statement executes once before the condition is tested

Tip:Usebreakstatement to break out of the loop, usecontinuestatement to skip the current iteration and continue with the next iteration.

Statement
while	Yes	Yes	Yes	Yes	Yes

while (condition) {
code block to be executed
}

Parameter	Description
condition	Required. Defines the condition for executing the loop. If it returns true, the loop continues; if it returns false, the loop stops. Note:If your condition is always true, the loop will never end. This may cause the browser to crash. Note:If you forget to increase the value of the variable used in the condition, the loop will never end. This may cause the browser to crash.

JavaScript Version:	1.0

Loop through the indexes of an array, and output the car names:

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

Example explained:

Implementation: we set a variable before the loop starts (var i = 0;)
Then, we define the condition for the loop. It runs until the variable i is less than the array length (4)
Each time the loop executes, the variable increments by 1 (i++)
Once the variable is no longer less than (the array length), the condition becomes false, and the loop terminates.