xkcd keyboard nav - Navigate xkcd with your keyboard

xkcd_keyboard_nav.user.js

/* xkcd keyboard nav - Navigate xkcd with your keyboard
 * 
 * Copyright (c) 2015-2018 Adrian Iain Lam <me@adrianiainlam.tk>
 * 
 * This program is free software. It comes without any warranty, to
 * the extent permitted by applicable law. You can redistribute it
 * and/or modify it under the terms of the Do What The Fuck You Want
 * To Public License, Version 2, as published by Sam Hocevar. See
 * http://www.wtfpl.net/txt/copying/ for more details.
 *
 * +---------------+----------------+
 * |   Key         |   Navigates to |
 * +---------------+----------------+
 * | [right arrow] |     next comic |
 * | [left arrow]  | previous comic |
 * | [f]           |    first comic |
 * | [l]           |     last comic |
 * | [r]           |   random comic |
 * +---------------+----------------+
 *
 * This script uses keyboardEvent.key, which may not be supported by
 * your browser. I have no intention to write a compatible script
 * with keyboardEvent.keyCode as it is deprecated anyway.
 */

// ==UserScript==
// @name        xkcd keyboard nav
// @namespace   https://github.com/adrianiainlam
// @description Navigate xkcd with your keyboard
// @version     1.0.4
// @downloadURL https://gist.github.com/adrianiainlam/542dd0794a874ca31321/raw/xkcd_keyboard_nav.user.js
// @updateURL   https://gist.github.com/adrianiainlam/542dd0794a874ca31321/raw/xkcd_keyboard_nav.user.js
// @include     /^https?://xkcd\.com(/[0-9]+)?/?$/
// @grant       none
// ==/UserScript==

function showTitleText() {
  var elem    = document.getElementById("comic");
  var child   = elem.children[0];
  var newnode = document.createElement("p");
  if(child instanceof HTMLImageElement) {
      newnode.appendChild(document.createTextNode(child.title));
  } else if(child instanceof HTMLAnchorElement && child.children[0] instanceof HTMLImageElement) {
      newnode.appendChild(document.createTextNode(child.children[0].title));
  } else {
      console.log("Title text not found by this script. Please file a bug report with URL");
  }
  elem.appendChild(newnode);
}

document.body.addEventListener("keypress", function(e) {
  if (!(e.target instanceof HTMLBodyElement)) {
    return;
  }
  var navList = document.getElementsByClassName("comicNav")[0].children;
  if(!e.altKey && !e.ctrlKey && !e.metaKey && !e.shiftKey) {
    switch(e.key) {
      case "ArrowLeft": // prev
        document.location.href = navList[1].firstChild.getAttribute("href");
        break;
      case "ArrowRight": // next
        document.location.href = navList[3].firstChild.getAttribute("href");
        break;
      case "r": // random
        document.location.href = navList[2].firstChild.getAttribute("href");
        break;
      case "f": // first
        document.location.href = navList[0].firstChild.getAttribute("href");
        break;
      case "l":  // last
        document.location.href = navList[4].firstChild.getAttribute("href");
        break;
    }
  }
});

showTitleText();