JSFiddle - React, Tailwind, and code Playground

HTML

<html>

<head>
    <script src="https://code.jquery.com/jquery-1.12.4.js"></script>
    <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
    <link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
</head>

    <body>
    
    Date: <input id="iDate">

    </body>

</html>

JavaScript

var eventDates = ["28/1/2018", "27/1/2018", "2/2/2018"];

$(function() {
    $("#iDate").datepicker({
    beforeShowDay : function(date) {
        var disDate = date.getDate();
        var disMonth = date.getMonth();
        var disYear = date.getFullYear();

        var formattedDate = disDate + "/" + (disMonth + 1) + "/" + disYear;

        if ($.inArray(formattedDate, eventDates) != -1) {
            return[false]
        } else {
            return[true]
        }

    }        
    });
});