var onkeydown = (function (ev) {

  var key;

  var isShift;

  if (window.event) {

    key = window.event.keyCode;

    isShift = !!window.event.shiftKey; // typecast to boolean

  } else {

    key = ev.which;

    isShift = !!ev.shiftKey;

  }

  if ( isShift ) {

    switch (key) {

      case 16: // ignore shift key

        break;

      default:

        alert(key);

        // do stuff here?

        break;

    }

  }

});