function(num) {
  if (num == 0) {
    return document.getElementById("EndPath")
  }
  return document.getElementById("Path" + num);
};

var navigateTo = function(up) {
  var numItems = document.querySelectorAll(
      ".line > .msgEvent, .line > .msgControl").length;
  var currentSelected = findNum();
  var newSelected = move(currentSelected, up, numItems);
  var newEl = numToId(newSelected, numItems);

  // Scroll element into center.
  scrollTo(newEl);
};

window.addEventListener("keydown", function (event) {
  if (event.defaultPrevented) {
    return;
  }
  // key 'j'
  if (event.keyCode == 74) {
    navigateTo(/*up=*/false);
  // key 'k'
  } else if (event.keyCode == 75) {
    navigateTo(/*up=*/true);
  } else {
    return;
  }
  event.preventDefault();
}, true);
</script>