While Loop

while repeats as long as its condition is true. Use it when you don't know in advance how many times to loop.

let countdown = 3;
while (countdown > 0) {
  console.log(countdown);
  countdown--;
}
console.log("Lift off!");

3
2
1
Lift off!

do...while

Runs the body at least once, then checks the condition.

let n = 10;
do {
  console.log(n);
  n++;
} while (n < 5);

10