Backslash key code is recognized as german umlaut

Question

I use onkeydown event and read pressed key from event object:

function test(e) {
   e = e || window.e;
   var keyCode = e.which || e.keyCode;

   alert(keyCode +' -> '+ String.fromCharCode(keyCode));
}

Above function works weird if user press backslash key (\) - it always return Ü instead of \. Value of e.keyCode is 220 what means that everything is ok, so probably fromCharCode() is an issue. I think that the problem is a fact that backslash is a special character. But how can I omit it and display proper char for 220 code?

I have made live example on JSFiddle.

Answer 1

Problem here is that you try to match keyboard key code to actual letter of keyboard layout.

E.g (test keyboard key code):

1. My keyboard layout is en-US
2. I press 2 and key code is 50
3. I change keyboard layout (or keyboard language) to lt-LT
4. I now press same key, but now it should output č, but key code is still 50.

---

You should have some some letter-to-key-code map, but you will never match all keyboard layouts.

function displayKeyCode(evt) {
  var textBox = getObject('txtChar');
  var charCode = (evt.which) ? evt.which : event.keyCode
  textBox.value = String.fromCharCode(charCode);
  if (charCode == 8) textBox.value = "backspace"; //  backspace
  if (charCode == 9) textBox.value = "tab"; //  tab
  if (charCode == 13) textBox.value = "enter"; //  enter
  if (charCode == 16) textBox.value = "shift"; //  shift
  if (charCode == 17) textBox.value = "ctrl"; //  ctrl
  if (charCode == 18) textBox.value = "alt"; //  alt
  if (charCode == 19) textBox.value = "pause/break"; //  pause/break
  if (charCode == 20) textBox.value = "caps lock"; //  caps lock
  if (charCode == 27) textBox.value = "escape"; //  escape
  if (charCode == 33) textBox.value = "page up"; // page up, to avoid displaying alternate character and confusing people          
  if (charCode == 34) textBox.value = "page down"; // page down
  if (charCode == 35) textBox.value = "end"; // end
  if (charCode == 36) textBox.value = "home"; // home
  if (charCode == 37) textBox.value = "left arrow"; // left arrow
  if (charCode == 38) textBox.value = "up arrow"; // up arrow
  if (charCode == 39) textBox.value = "right arrow"; // right arrow
  if (charCode == 40) textBox.value = "down arrow"; // down arrow
  if (charCode == 45) textBox.value = "insert"; // insert
  if (charCode == 46) textBox.value = "delete"; // delete
  if (charCode == 91) textBox.value = "left window"; // left window
  if (charCode == 92) textBox.value = "right window"; // right window
  if (charCode == 93) textBox.value = "select key"; // select key
  if (charCode == 96) textBox.value = "numpad 0"; // numpad 0
  if (charCode == 97) textBox.value = "numpad 1"; // numpad 1
  if (charCode == 98) textBox.value = "numpad 2"; // numpad 2
  if (charCode == 99) textBox.value = "numpad 3"; // numpad 3
  if (charCode == 100) textBox.value = "numpad 4"; // numpad 4
  if (charCode == 101) textBox.value = "numpad 5"; // numpad 5
  if (charCode == 102) textBox.value = "numpad 6"; // numpad 6
  if (charCode == 103) textBox.value = "numpad 7"; // numpad 7
  if (charCode == 104) textBox.value = "numpad 8"; // numpad 8
  if (charCode == 105) textBox.value = "numpad 9"; // numpad 9
  if (charCode == 106) textBox.value = "multiply"; // multiply
  if (charCode == 107) textBox.value = "add"; // add
  if (charCode == 109) textBox.value = "subtract"; // subtract
  if (charCode == 110) textBox.value = "decimal point"; // decimal point
  if (charCode == 111) textBox.value = "divide"; // divide
  if (charCode == 112) textBox.value = "F1"; // F1
  if (charCode == 113) textBox.value = "F2"; // F2
  if (charCode == 114) textBox.value = "F3"; // F3
  if (charCode == 115) textBox.value = "F4"; // F4
  if (charCode == 116) textBox.value = "F5"; // F5
  if (charCode == 117) textBox.value = "F6"; // F6
  if (charCode == 118) textBox.value = "F7"; // F7
  if (charCode == 119) textBox.value = "F8"; // F8
  if (charCode == 120) textBox.value = "F9"; // F9
  if (charCode == 121) textBox.value = "F10"; // F10
  if (charCode == 122) textBox.value = "F11"; // F11
  if (charCode == 123) textBox.value = "F12"; // F12
  if (charCode == 144) textBox.value = "num lock"; // num lock
  if (charCode == 145) textBox.value = "scroll lock"; // scroll lock
  if (charCode == 186) textBox.value = ";"; // semi-colon
  if (charCode == 187) textBox.value = "="; // equal-sign
  if (charCode == 188) textBox.value = ","; // comma
  if (charCode == 189) textBox.value = "-"; // dash
  if (charCode == 190) textBox.value = "."; // period
  if (charCode == 191) textBox.value = "/"; // forward slash
  if (charCode == 192) textBox.value = "`"; // grave accent
  if (charCode == 219) textBox.value = "["; // open bracket
  if (charCode == 220) textBox.value = "\\"; // back slash
  if (charCode == 221) textBox.value = "]"; // close bracket
  if (charCode == 222) textBox.value = "'"; // single quote
  var lblCharCode = getObject('spnCode');
  lblCharCode.innerHTML = 'KeyCode:  ' + charCode;
  return false;
}

function getObject(obj) {
  var theObj;
  if (document.all) {
    if (typeof obj == 'string') {
      return document.all(obj);
    } else {
      return obj.style;
    }
  }
  if (document.getElementById) {
    if (typeof obj == 'string') {
      return document.getElementById(obj);
    } else {
      return obj.style;
    }
  }
  return null;
}

<input onkeypress="javascript:return false;" id="txtChar" onkeydown="javascript:return displayKeyCode(event)" name="txtChar" type="text"/><br/>
<span id="spnCode"></span>