JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.min.js"></script>
<link rel="stylesheet" href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>
<form method="POST">
  <div style='margin:0 auto; text-align:center;'>
    <label>Appointment Date: </label>
    <input type="hidden" name="action" value="list_appointments" />
    <input type="text" id="datepicker" name="date" class="datepicker" />
    <input type="submit" value="Refresh List" name="Update" />
    <br />
  </div>
</form>

JavaScript

$(document).ready(function() {
   $(".datepicker").datepicker({
     minDate: '0',
     changeMonth: true,
     changeYear: true,
     beforeShowDay: function(dt) {
       return [dt.getDay() === 2 || dt.getDay() === 3, ""];
     }
   });
 });

 function setDate() {
   var today = moment().isoWeekday(); //or just = new Date().getDay();
   if (today <= 2) {
     return moment().isoWeekday(2);
   } else if (today === 3) {
     return moment().isoWeekday(3);
   } else {
     return moment().add(1, 'weeks').isoWeekday(2);
   }
 }
 
 $('.datepicker').datepicker("setDate", new Date(setDate()));