Stop countdown when it reaches to "0"

Question

I want to stop this counter when it reaches to 0, can anyone help me?

function countdown() {
    var i = document.getElementById('counter');
    if (parseInt(i.innerHTML)<=0) {
    }
    i.innerHTML = parseInt(i.innerHTML)-1;
}
setInterval(function(){ countdown(); },1000);

Answer 1

You use the clearInterval function:

var id;
function countdown() {
    var i = document.getElementById('counter');
    if (parseInt(i.innerHTML)<=1) {
        clearInterval(id);
    }
    i.innerHTML = parseInt(i.innerHTML)-1;
}
id = setInterval(countdown,1000);