JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="showAsReservation('http://www.ucaknezaman.com'); return false;">
Test
</button>

JavaScript

var windowObjectReference = null; // global variable
    function showAsReservation(url){   	
    if(windowObjectReference == null || windowObjectReference.closed){
            windowObjectReference = window.open(url,
                "_blank","toolbar=no,scrollbars=no, resizable=yes, top=500, left=500, width=400, height=400");
          }
          else
          {
            windowObjectReference.focus();
          };
        windowObjectReference.focus();
    }