JavaScript While Loops Explained with Examples

The while loop starts by evaluating the condition. If the condition is true, the statement(s) is/are executed. If the condition is false, the statement(s) is/are not executed and the while loop ends. while loops deserve some attention, since you will create an infinite loop if the false condition is never met. An infinite loop can crash your application or browser, so make sure all the while loops in your code are finite.

Here is the syntax for the while loop:

Syntax:

while (condition) {
  statement(s);
}

statement(s): A statement that is executed as long as the condition evaluates to true.

condition: Here, condition is a Boolean expression which is evaluated before each pass through the loop. If this condition evaluates to true, statement(s) is/are executed. When condition evaluates to false, execution continues with the statement after the while loop.

Example:

let i = 1;
while (i < 10) {
  console.log(i);
  i++; // same as i = i + 1
}

Output:
1 
2 
3 
4
5
6
7
8
9

Example of an infite loop:

let x = 0;
while (x < 10) {
  console.log(x);
  x--; // same as i = i - 1
}

Output:
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
...etc.
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