ctrl+enter keyboard shortcut not working in firefox, how to fix?

Question

JavaScript

Wrote code to send an error message. When selected and pressed ctrl+enter, the function is called. It works in chrome but not in firefox. Help me please.
Here is the code:

document.onkeydown = function (e){
  var txt = '';
  if (txt = window.getSelection) {// Не IE, используем метод getSelection
    txt = window.getSelection().toString();
  } else { // IE, используем объект selection
    txt = document.selection.createRange().text;
  }

  if(e.keyCode == 17)
    ctrl = true;
  else if(e.keyCode == 13 && ctrl && txt != '')
    oFB_mistape.open( txt );
}

document.onkeyup = function (e){
  if(e.keyCode == 17)
    ctrl = false;
}

Answer 1

www.stackoverflow.com/a/1684236/1603055