1. This looks like a school assignment XD
2. Anyways:

let countdown = 3;
let loop = setInterval(function() {
if(countdown > 0){
countdown -= 1;
console.log(countdown)://Log the countdown
} else {
clearInterval(loop);//Stop looping
console.log('Blast off!');
}
},1000);//Repeat every second

i'm not sure about node.js, but you can make on in normal javascript.

https://stackoverflow.com/questions/20618355/the-simplest-possible-javascript-countdown-timer