JavaScript while loop (with examples and use cases)

The while statement is used to create a loop that continues to execute the statement as long as the condition evaluates to true. You are required to write both the condition and the statement.

Here’s the basic structure of the code:

while (condition) {
  statement;
}

Just like the for statement, the while loop is used to execute a piece of code over and over again until it reaches the desired condition.

The example below will keep executing the statement block until the condition expression returns false:

let i = 0;

while (i < 6) {
  console.log(`The value of i = ${i}`);
  i++;
}

Keep in mind that you need to include a piece of code that eventually turns the evaluating condition to false or the while loop will be executed forever. The example below will cause an infinite loop:

let i = 0;

while (i < 6) {
  console.log(`The value of i = ${i}`);
}

When to use while over for loop?

Seeing that both while and for can be used for executing a piece of code repeatedly, when should you use while loop instead of for?

An easy way to know when you should use while is when you don’t know how many times you need to execute the code.

Here’s a perfect example of a loop that can only be done with while:

You are required to random a number between 1 and 10 until you get the number 8. You also need to show how many times you execute the random method until number 8 is returned:

let randomResult = 0;
let loopCount = 0;

while (randomResult !== 8) {
  randomResult = Math.floor(Math.random() * (10 - 1 + 1) + 1);
  loopCount++;
}

console.log(`The random result: ${randomResult}`);
console.log(`The number of loops: ${loopCount}`);

Because you can’t know how many times you need to loop until you get the number 8, you need to use a while loop instead of a for loop.