JSFiddle - React, Tailwind, and code Playground

HTML

<table>
   
    <tr>
        <td>Works without warning in all browsers:</td>
        <td><input type="button" onclick="performSyncronousRequest()" value="Syncronous request"/><td>
    </tr>
   
    </tr>
</table>

JavaScript

/**
* This method will give open the popup without a warning.
*/
function performSyncronousRequest() {
    $.ajax({
     url: '/echo/html',
     data: {},
     success: function(){
         window.open('http://www.w3schools.com');
     },
     async: false
    });
}