Kanji Bigify

// ==UserScript==
// @name        Kanji Bigify
// @namespace   jklmnop.net
// @description Make Kanji/Kana Bigger!
// @include     *://*.4channel.org/*
// @include     *://*.4chan.org/*
// @exclude     *://twitter.com/*
// @exclude     *://www.dlsite.com/*
// @exclude     *://kirarafantasia.com/*
// @exclude     *://*.nyaa.si/*
// @version     1
// @grant       none
// ==/UserScript==


/*
 * Only works on 4chan/nel for now. Change the include line to just a * to make it work for everything.
 * Write sites with exclude to ignore them
 */

var kanjiClassName = 'kanjibigifier';

var kanjiCSS = [
  "." + kanjiClassName + " {",
  "font-size: 20px;",
  "}"
].join("");

var textPath = '//text()[not(ancestor::script) and not(ancestor::style)]';

var kRegex = /([\u2E80-\u2EFF\u2F00-\u2FDF\u3000-\u303F\u3040-\u309F\u30A0-\u30FF\u31C0-\u31EF\u3200-\u32FF\u3300-\u33FF\u3400-\u4DBF\u4E00-\u9FFF]+)/g;

function addGlobalStyle(css) {
  try {
    var elmHead, elmStyle;
    elmHead = document.getElementsByTagName('head')[0];
    elmStyle = document.createElement('style');
    elmStyle.type = 'text/css';
    elmHead.appendChild(elmStyle);
    elmStyle.innerHTML = css;
  } catch (e) {
    if (!document.styleSheets.length) {
      document.createStyleSheet();
    }
    document.styleSheets[0].cssText += css;
  }
}

addGlobalStyle(kanjiCSS);

var snapTextElements = document.evaluate(
  textPath,
  document,
  null,
  XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
  null
);

for (var i = snapTextElements.snapshotLength - 1; i >= 0; i--) {
  var elmText = snapTextElements.snapshotItem(i);
  if (kRegex.test(elmText.nodeValue)) {
    var elmSpan = document.createElement("span");
    var sText = elmText.nodeValue;
    elmText.parentNode.replaceChild(elmSpan, elmText);
    kRegex.lastIndex = 0;
    for (var match = null, lastLastIndex = 0;
       (match = kRegex.exec(sText)); ) {
      elmSpan.appendChild(document.createTextNode(
      sText.substring(lastLastIndex, match.index)));
      var elmKanjiSpan = document.createElement("span");
      //elmLink.setAttribute("href", match[0]);
      elmKanjiSpan.setAttribute("class", kanjiClassName);
      elmKanjiSpan.appendChild(document.createTextNode(match[0]));
      elmSpan.appendChild(elmKanjiSpan);
      lastLastIndex = kRegex.lastIndex;
    }
    elmSpan.appendChild(document.createTextNode(
      sText.substring(lastLastIndex)));
    elmSpan.normalize();
  }
}