creating timer and endings timer javascript code example

Example 1: function countDown() 21 SEC

var seconds = document.getElementById("countdown").textContent;
var countdown = setInterval(function() {
    seconds--;
    document.getElementById("countdown").textContent = seconds;
    if (seconds <= 0) clearInterval(countdown);
}, 1000);

Example 2: javascript get clock time in auto counter up

function display_ct() {
var x = new Date()
var x1=x.getMonth() + 1+ "/" + x.getDate() + "/" + x.getYear(); 
x1 = x1 + " - " +  x.getHours( )+ ":" +  x.getMinutes() + ":" +  x.getSeconds();
document.getElementById('ct').innerHTML = x1;
display_c();
 }