javascript setInterval()

js:

setInterval(function () {

    var currentdate = new Date();

    var datetime = currentdate.getDate() + "/" + (currentdate.getMonth() + 1) + "/" + currentdate.getFullYear() + " @ " + currentdate.getHours() + ":" + currentdate.getMinutes() + ":" + currentdate.getSeconds();



    var target_matches = document.querySelectorAll('.target-timeout');

    target_matches[0].innerHTML = datetime;

}, 1000);

html:

<h3>update date and time every second</h3>

<h3 class="target-timeout"></h3>