JSFiddle - React, Tailwind, and code Playground

JavaScript

$(document).ready(function () {

var d = new Date();

            var monthNames = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
         
     
             var pastmonth = monthNames[(d.getMonth() - 1)%12].toString();
                  alert('Past Month: ' + pastmonth);
     
     
            var monthlymonth = monthNames[(d.getMonth())%12].toString();
                  alert('Current Month: ' + monthlymonth);
     
     
            var futuremonth = monthNames[(d.getMonth() + 1)%12].toString();
                  alert('Future Month: ' + futuremonth);
            //Error over here and I am not sure why
     
     
 });