We can use below method:

function doesConnectionExist() {
    var xhr = new XMLHttpRequest();
    var file = "https://www.kirupa.com/blank.png";
    var randomNum = Math.round(Math.random() * 10000);
 
    xhr.open('HEAD', file + "?rand=" + randomNum, true);
    xhr.send();
    
    xhr.addEventListener("readystatechange", processRequest, false);
 
    function processRequest(e) {
      if (xhr.readyState == 4) {
        if (xhr.status >= 200 && xhr.status < 304) {
          alert("connection exists!");
        } else {
          alert("connection doesn't exist!");
        }
      }
    }
}