Count selection's characters and lines

//GreaseMonkey: Count selection's characters and lines
//2019-01-03, https://greasyfork.org/en/users/85671-jcunews

(function(displayTime, disp, timer) {
  function dispClose(ev) {
    if (ev) ev.preventDefault();
    if (!disp) return;
    clearTimeout(timer);
    disp.remove();
    disp = null;
  }

  displayTime = 2000; //in milliseconds. 1000ms = 1 second

  addEventListener("keydown", function(ev, txt, msg) {

    //shortcut: CTRL+; without SHIFT or ALT
    if (!(ev.ctrlKey && !ev.shiftKey && !ev.altKey && (ev.key.toLowerCase() === ";"))) {

      //when the message is displayed, keys except CTRL, SHIFT, or ALT, or the CTRL+L shortcut, will close the message
      if (disp && !["control", "shift", "alt"].includes(ev.key.toLowerCase())) dispClose(ev);
      return;
    }

    ev.preventDefault();
    if (disp) return;
    txt = getSelection();
    if ((txt.anchorNode === txt.focusNode) && (txt.anchorOffset === txt.focusOffset)) {
      if (!(txt = document.activeElement) || !("value" in txt)) return;
      txt = txt.value.substring(txt.selectionStart, txt.selectionEnd);
    } else txt = txt.toString();
    if (txt) {
      msg = txt.length + " characters.";
    } else {
      msg = "No selection.";
    }
    if (disp) {
      clearTimeout(timer);
      disp.remove();
    }
    disp = document.createElement("DIV");
    disp.innerHTML = '<div style="margin:13% auto;border:2px solid blue;width:15ex;text-align:center;padding:1ex 1.5ex;background-color:white;color:black;white-space:pre;font-size:16pt;line-height:normal">' + msg + '</div>';
    disp.style.cssText = "position:fixed;z-index:999999;left:0;top:0;right:0;bottom:0;background-color:rgb(1,1,1,0.3);cursor:pointer";
    disp.onclick = dispClose;
    document.body.appendChild(disp);
    disp.contentEditable = false;
    setTimeout(dispClose, displayTime);
  });
})();