history scroll by shortcut key (Redmine view customize plugin)

gistfile1.js

$(function() {

  var KEYCODE_J = 74;
  var KEYCODE_K = 75;

  var EXCEPT_TAG_NAMES = ['input', 'textarea', 'select'];

  var targetElements = $('#history > div');
  var currentIndex = -1;

  document.addEventListener(
   'keydown',
   function(event) {

     if (EXCEPT_TAG_NAMES.indexOf(event.target.tagName.toLowerCase()) != -1) {
       return;
     }

     if (event.keyCode != KEYCODE_J && event.keyCode != KEYCODE_K) {
       return;
     }

     var nextIndex =
             currentIndex + ((event.keyCode == KEYCODE_J) ? 1 : -1);
 
     if (nextIndex < 0) {
       nextIndex = 0;
     } else if (nextIndex >= targetElements.length) {
       nextIndex = targetElements.length - 1;
     }

     targetElements.css('border', '');

     targetElements[nextIndex].scrollIntoView();
     targetElements.eq(nextIndex).css('border', '3px solid #d7d7d7');
     currentIndex = nextIndex;
   });
})