WordPress Shortcode countdown clock using FlipClock.js

sls-countdown-flipper-clock.php

<?php
/* Need to include flipclock.js's css and js files. Instructions found on their github page
 * http://flipclockjs.com
 * 
 */
// Flipper countdown function
function sls_flipper_countdown($atts){
  // Attributes - For the End Date
    extract( shortcode_atts(
        array(
            'end_date' => '',
            'end_time' => '',           
        ), $atts )
    );
    // code
    ob_start();
    $output = '
  
      <p class="countdown-timer"></p>
          
      <script src="/flipclock/compiled/flipclock.min.js"></script>
      <script type="text/javascript">
        var countDownDate = new Date("'.esc_attr($end_date).' '.esc_attr($end_time).'").getTime();
        var now = new Date().getTime();
          
          // Find the distance between now and the count down date
          var distance = countDownDate/1000 - now/1000;

        var clock = jQuery(\'.countdown-timer\').FlipClock(distance, {
          clockFace: \'DailyCounter\',
          countdown: true,
          showSeconds: false
        });
      </script>
    ';

    $output .= ob_get_contents();
    ob_end_clean();
    return $output;
}

add_shortcode('course-countdown','sls_flipper_countdown');