JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://code.jquery.com/ui/1.9.0/themes/base/jquery-ui.css">
<script src="http://code.jquery.com/ui/1.9.0/jquery-ui.js"></script>
<div id="datepicker"></div>

CSS

.ui-datepicker td.my_cell_highligth a{background:yellow;}

JavaScript

var a_date_array = [1,4,6,7,15,24]

$( "#datepicker" ).datepicker({
    dateFormat: 'yy-mm-dd',
    beforeShowDay: function(d_date){
        console.log(d_date);
        //Here compare your Date Array and the d_date
        var d_picker = new Date(d_date);
        var s_class_highligth = '';
        if($.inArray(d_picker.getDate(),a_date_array)>-1){
            s_class_highligth = 'my_cell_highligth';
        }
        
        return [true, s_class_highligth, 'this is optional tooltip'];
    }
});