JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.simpleWeather/3.1.0/jquery.simpleWeather.min.js"></script>
<div id="weather">

</div>

JavaScript

var spanId;
var i = 0;
var days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
var tomorrow = new Date();
var newdate = new Date();





for (i = 1; i < 8; i++) {
  //alert("day" + i);
	weatherForecastID = 'day'+i;
  newdate.setDate(tomorrow.getDate() + i);
  //alert(newdate);
  //alert(newdate.getDate() + '/' + (newdate.getMonth() + 1) + '/' + newdate.getFullYear());
  alert(days[newdate.getDay()]);
  alert(weatherForecastID);

}