keyboard key ascii values

<script type="text/javascript">
document.onkeyup = KeyCheck;

function KeyCheck()
{
   var KeyID = event.keyCode;
   switch(KeyID)
   {
      case 16:
      document.Form1.KeyName.value = "Shift";
      break; 
      case 17:
      document.Form1.KeyName.value = "Ctrl";
      break;
      case 18:
      document.Form1.KeyName.value = "Alt";
      break;
      case 19:
      document.Form1.KeyName.value = "Pause";
      break;
      case 37:
      document.Form1.KeyName.value = "Arrow Left";
      break;
      case 38:
      document.Form1.KeyName.value = "Arrow Up";
      break;
      case 39:
      document.Form1.KeyName.value = "Arrow Right";
      break;
      case 40:
      document.Form1.KeyName.value = "Arrow Down";
      break;
   }
}