While Loops

What is a while loop?

The “while loop” is executed as long as the specified condition is true.
Inside the while loop, you should include the statement that will end the loop at some point of time. Otherwise, your loop will never end and your browser may crash.

Example:

The JavaScript code below displays the numbers 1 through 5 with a loop
Notice we have a variable with a starting value which is i = 1
And we have a condition for the loop. The loop will run only if the variable i is less than or equals to 5
Then we increase the variable inside the loop every time the loop runs, like a count.
If we don't change the value of the variable i inside the loop, it will become an infinite loop (unending loop) and the program will crash (stop working).

Try the code example below in the code editor:

In the code below, we use a while loop to display (on a webpage) all even numbers below 20 starting from 2 (that's why we have a variable i = 2 before the loop).
Notice we use the condition "i<20" to know when to stop and we increase the variable "i" inside the loop to update the count.

The output should look like this:

Note:

If you want to display all even numbers below 100, all you have to do is to simply change the condition to "i<100" and the code will work with the same code.
That's how loops save time; you can use a couple lines of code to repeat the same actions many many times.

Decreasing Count:

You can use a while loop with a decreasing count.

Try the code in the screenshot above in your code editor!

Expected Outcome:

Loops in JS - Part 1