get the name of month without using hard coded arrays in javascript

1'use strict';
2
3(function(d){
4    var mL = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];
5    var mS = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'June', 'July', 'Aug', 'Sept', 'Oct', 'Nov', 'Dec'];
6
7    d.prototype.getLongMonth = d.getLongMonth = function getLongMonth (inMonth) {
8        return gM.call(this, inMonth, mL);
9    }
10
11    d.prototype.getShortMonth = d.getShortMonth = function getShortMonth (inMonth) {
12        return gM.call(this, inMonth, mS);
13    }
14
15    function gM(inMonth, arr){
16        var m;
17
18        if(this instanceof d){
19            m = this.getMonth();
20        }
21        else if(typeof inMonth !== 'undefined') {
22            m = parseInt(inMonth,10) - 1; // Subtract 1 to start January at zero
23        }
24
25        return arr[m];
26    }
27})(Date);
28

1//Assume that cuurent month is December results are given
2
3var getmonth  = new Date().toLocaleString("en-us", { month: "short" });
4console.log(getmonth);
5//result =Dec
6
7
8var getmonth  = new Date().toLocaleString("en-us", { month: "long" });
9console.log(getmonth);
10
11//result= December
12
13
14var getmonth  = new Date().toLocaleString("en-us", { month: "narrow" });
15console.log(getmonth);
16
17//result=D