AndroidBuildstringConverter.js

var AndroidBuildstringConverter = {
    DayZero: new Date(2009, 0, 1),
    ReleaseNames: "Astro Boy;Bender;Petit Four;Cupcake;Donut;Eclair;Froyo;Gingerbread;" +
            "Honeycomb;Ice Cream Sandwich;Jelly Bean;KitKat;Lollipop;Marshmallow;Nougat",
    getBuilddateByString: function (b) {
        if ("string" !== typeof b || !b.length) {
            return console.log("Invalid input. String required, got " + typeof b),
            !1;
        }
        var c = this.ReleaseNames.split(";").pop()[0],
            e = {};
        if (b[0].toUpperCase() > c || "C" > b[0].toUpperCase()) {
            return console.log("Invalid build string. 1st char must be between C and " + c),
            !1;
        }
        var c = this.ReleaseNames.split(";");
        for (var d in c.reverse()) {
            if (b[0].toUpperCase() == c[d][0].toUpperCase()) {
                e.releaseName = c[d];
                break;
            }
        }
        if ("P" !== b[1].toUpperCase() && "R" !== b[1].toUpperCase()) {
            return console.log("Invalid build string. 2nd char must be either R (Release) or P (Preview). Got " + b[1].toUpperCase()),
            !1;
        }
        e.buildBranch = "R" === b[1].toUpperCase()
            ? "Release"
            : "Preview";
        console.dir(e);
        return e;
    },
    getBuildstringByDate: function (b, c) {
        var e = this.ReleaseNames.split(";").pop()[0],
            e = e + (!1 === c
                ? "P"
                : "R");
        c = /object Date/.test(Object.prototype.toString.call(b))
            ? b
            : "string" === typeof b && b.length
                ? new Date(Date.parse(b + " UTC+0000"))
                : new Date;
        for (var d = this.DayZero, d = 12 * (c.getUTCFullYear() - d.getUTCFullYear()) + (c.getUTCMonth() - d.getUTCMonth()) + 1, d = Math.round(d / 3); 26 < d;) {
            d -= 26;
        }
        e += String.fromCharCode(64 + d);
        m = c.getUTCMonth();
        m = 3 < m
            ? 9 <= m
                ? 9
                : 6 <= m
                    ? 6
                    : 3
            : 0;
        m = new Date(c.getUTCFullYear(), m, 1);
        return e + ("" + (Math.floor((c - m) / 86400000) + 1));
    }
};
    
var a = AndroidBuildstringConverter.getBuilddateByString('NPG05'); 
console.dir(a);

var a = AndroidBuildstringConverter.getBuildstringByDate(); // Today's build string
console.dir(a);

a = AndroidBuildstringConverter.getBuildstringByDate(null, false); // Today's build string; but for Preview builds
console.dir(a);

var dt = new Date(2017, 0, 11); // Optionally, pass a JavaScript Date object to specify a date.
a = AndroidBuildstringConverter.getBuildstringByDate(dt); // Build string for Apr 11th 2017
console.dir(a);

dt = '2017/1/11'; // Or, instead of a Date object, you can also pass a string.
a = AndroidBuildstringConverter.getBuildstringByDate(dt); // Build string for Apr 11th 2017
console.dir(a);

dt = '2017-01-11'; // String format is 'flexible', btw. So no need to format yourself.
a = AndroidBuildstringConverter.getBuildstringByDate(dt); // Build string for Apr 11th 2017
console.dir(a);