Add HTML and missing day
and append at the end before assignment
var d = new Date();
var day;
switch (d.getDay()) {
case 0:
day = "Sunday";
break;
case 1:
day = "Monday";
break;
case 2:
day = "Tuesday";
break;
case 3:
day = "Wednesday";
break;
case 4:
day = "Thursday";
break;
case 5:
day = "Friday";
break;
default:
day = "Saturday";
}
document.getElementById("demo").innerHTML = "Today is : " + day;
<div id="demo"></div>