immediately load images w/ PagerExtention for UserScript

g-lii.user.js

// ==UserScript==
// @name        Load Image Immediately
// @namespace   http://noromanba.flavors.me
// @description images immediately load w/ PagerExtention for UserScript
// @include     *://gigazine.net/*
// @include     *://www.moae.jp/comic/*
// @include     *://omocoro.jp/*
// @include     *://rocketnews24.com/*
// @grant       none
// @noframes
// @run-at      document-end
// @version     2017.3.10.0
// @homepage    https://gist.github.com/noromanba/d6401655958f3d553589
// @downloadURL https://gist.github.com/noromanba/d6401655958f3d553589/raw/g-lii.user.js
// @contributor to    https://gist.github.com/to/5334394
// @contributor dlwr  https://gist.github.com/dlwr/39f87b3f07229c7d5ce9
// @org-license Unknown (as-is)
// @license     TBD (as-is)
// @icon        https://upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Toilet_paper_roll_revisited.svg/128px-Toilet_paper_roll_revisited.svg.png
// ==/UserScript==

// Icon (CC0 by PeterM)
// https://commons.wikimedia.org/wiki/File%3AToilet_paper_roll_revisited.svg

// Devel
// https://gist.github.com/noromanba/d6401655958f3d553589


(() => {
  // c.f. jQuery.lazyload
  // https://www.appelsiini.net/projects/lazyload
  // https://github.com/tuupola/jquery_lazyload
  const immediate = (img) => {
    img.src =
      img.dataset.original ||
      img.dataset.src ||
      img.dataset.lazySrc ||
      img.src;
  };

  const loadImmediate = (ctx = document.body) => {
    if (!ctx.querySelectorAll) return;

    if (ctx.nodeName.toLowerCase() === 'img') {
      immediate(ctx);
    } else {
      Array.from(ctx.querySelectorAll('img'), img => {
        immediate(img);
      });
    }
  };
  loadImmediate(document.body);

  new MutationObserver(records => {
    records.forEach(record => {
      // TBD omit addedNodes
      Array.from(record.addedNodes, node => {
        loadImmediate(node);
      });
    });
  }).observe(document.body, { childList: true, subtree: true });
})();