Pop up/ child window property "closed" is always true when the window is actually open in IE 11 and other lower versions

Question

// open new pop up window

this.childWindow = window.open("about:blank", "_blank");   


this.childWindow.document.write("<p>Loading..</p>");

this.childWindow.focus();

// submit form to cross origin domain from the pop up

this.childWindow.document.write("<form name='xform' method='POST' action='" + this.url + "' enctype='multipart/form-data'><input class='form-control' type='hidden' name='msg' id='xml'></input><input class='form-control' type='submit' id='formSubmit' style='display:none' ></input></form>");   

this.childWindow.document.getElementById('xml').value = response.message;

this.childWindow.document.getElementById('formSubmit').click();

// window closed event

this.timer = setInterval(() => {

  if (this.childWindow && this.childWindow.closed) {

 // logic here when window closed

    clearInterval(this.timer);
  }
}, 1000);