I don't know why my function is not properly called every 100 milliseconds. It is just called once, when the page is loaded/reloaded. I am out of ideas what to try.
var unit = document.getElementsByClassName('unit');
var date = new Date();
function setTime() {
hour.textContent = date.getHours();
unit[0].textContent = "h";
minute.textContent = date.getMinutes();
unit[1].textContent = "m";
console.log('boom');
}
setInterval(setTime, 100);<h1 id="time">
<span id="hour"></span><!--
--><span class="unit"></span>
<span id="minute"></span><!--
--><span class="unit"></span>
</h1>