While Loop

The first type of loop we will look at is the while loop. Imagine you want to print the numbers 1-100. Doing this manually would take a long time. We can simplify this using a while loop:

let number = 1;
while (number <= 100) { // While number is less than or equal to 100
	console.log(number); // Print number
	number = number + 1; // Increase number by 1
}

You can see that the while loop has a similar structure to the if statement.

It works as follows: after the word while comes a condition which, as long as it is true, the block of code inside the while loop will repeat. To remind you, a block of code is the code inside curly braces {} following statements like if, else, or while.

Our code will perform the following steps:

1. Set the value of the variable number to 1.
2. Check if number is less than or equal to 100.
3. If yes, print the value of the variable number, increase its value by 1, and return to step 2.
4. If not, the program will end.

Notice that if we forgot to increase number by 1 in our loop, number would always be 1, and our loop would repeat indefinitely. This would cause a program that does not respond and would probably terminate itself after a while. This is always undesirable, and as programmers, we must be careful to avoid this error.