while loops

while repeats

• while (test) { ... } runs again and again, as long as the test stays true.
• It checks the test before each pass — so the body might run zero times.

let n = 1;
while (n <= 3) {
  console.log(n);   // → 1, then 2, then 3
  n++;
}

Make progress every pass

• Something inside must move the test toward false.
• If nothing changes, the loop never stops — an infinite loop (the Stop button saves you).

let n = 1;
while (n < 50) {
  n = n * 2;   // 2, 4, 8, 16, 32, 64 — then stop
}
console.log(n);   // → 64

Common mistakes

• Change the condition inside the loop, or it runs forever.
• A while checks its condition first, so it may run zero times.

Now you try

• Use a while loop.
• Press Check answer to test it.