Edit in JSFiddle

function genPopup() {
  var popup = window.open("", "daynhauhoc", "width=300,height=100");

  if (popup) {
    popup.document.body.innerHTML = '<form><input type="textbox" name="itemname" /> <input type="submit" value="OK" /></form><a href="javascript:window.close();">Close window</a>';
    popup.document.title = popup.name;

    popup.document.getElementsByTagName("FORM")[0].onsubmit = function(e) {
      e.preventDefault();

      popup.opener.document.getElementById('output').innerHTML = this.itemname.value;
      popup.close();
    }
  } else {
    document.body.innerHTML = "<p>Popup is blocked!</p>";
  }
}
// genPopup();

<button onclick="genPopup();">Run</button>
<p id="output"></p>