JSFiddle - React, Tailwind, and code Playground

by Roko

HTML

<script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
<link rel="stylesheet" href="http://t1m0n.name/air-datepicker/dist/css/datepicker.min.css">
<script src="http://t1m0n.name/air-datepicker/dist/js/datepicker.js"></script>
<input type="text"
    data-range="true"
    data-multiple-dates-separator=" - "
    id="my-element">

CSS

.-current-week- {
  background: red;
}

JavaScript

function getWeek(d) {
  // https://stackoverflow.com/a/6117889/383904
  d = new Date(Date.UTC(d.getFullYear(), d.getMonth(), d.getDate()));
  d.setUTCDate(d.getUTCDate() + 4 - (d.getUTCDay()||7));
  var yearStart = new Date(Date.UTC(d.getUTCFullYear(),0,1));
  var weekNo = Math.ceil(( ( (d - yearStart) / 86400000) + 1)/7);
  return {year:d.getUTCFullYear(), number: weekNo};
}

var currentWeekNumber = getWeek(new Date()).number;

$('#my-element').datepicker({
  onRenderCell: function(date, cellType) {
    if (cellType === 'day' && getWeek(date).number === currentWeekNumber) {
      return {
        classes: '-current-week-',
      }
    }
  }
});