How to set count down timer in JavaScript

Question

I want to set a timer for 30 minutes and it should count down and come to 0 using java script
I used setInterval() and setTimeout() but it is not working

Answer 1

function myTimeoutFunction() {
doStuff();
setTimeout(myTimeoutFunction, 1000); } myTimeoutFunction();

Answer 2

setInterval(function(){
doStuff()
}, 1000);

Answer 3

you can check my first code here(Session Timer),it's all about intervals using only native js,maybe it will help you to undestand how things work...
It was my first js experiments :D

Answer 4

show your code with setInterval

Answer 5

function doStuff() {
alert("go to next");

}