$("#txtboxToFilter").keydown(function(event) {
 
  if ((event.keyCode == 8           // backspace
        || event.keyCode == 46    // delete
        || (event.keyCode >= 48 && event.keyCode <= 57)   // numbers on keyboard
        || (event.keyCode >= 96 && event.keyCode <= 105))// number on keypad
        ) {
           // Do Something
    }
});