Javascript date functions

Day name by given date :

Day Name :

<script>
function firstview() {
var day=document.getElementById("txtfirstday").value;
var month=document.getElementById("txtfirstMonth").value;
var year=document.getElementById("txtfirstyear").value;
var date=month+'/'+day+'/'+year
    var d = new Date(date);

    var weekday = new Array(7);
    weekday[0] = "Sunday";
    weekday[1] = "Monday";
    weekday[2] = "Tuesday";
    weekday[3] = "Wednesday";
    weekday[4] = "Thursday";
    weekday[5] = "Friday";
    weekday[6] = "Saturday";

    var n = weekday[d.getDay()];
document.getElementById("divfristviewresult").style.display="block"
    document.getElementById("spndayName").innerHTML = n;
}
</script>


<br />
<div>
<h2>
Given date by day name :</h2>
<input id="txtfirstday" placeholder="day" type="number" />
<input id="txtfirstMonth" placeholder="Month" type="number" />
<input id="txtfirstyear" placeholder="year" type="number" />
<input id="btnfirstbutton" onclick="firstview()" type="button" value="Submit" />
</div>
<div id="divfristviewresult" style="display: none;">
Day Name : <b><span id="spndayName"></span> </b><br />
<div>
</div>