chatwork-image-extractor.user.js

// ==UserScript==
// @name           ChatWork Image Extractor
// @description    Image extractor for ChatWork.
// @include        https://www.chatwork.com/*
// @version        0.0.1
// ==/UserScript==

(function() {
  var forEach = Array.prototype.forEach,
  ATTR_NAME_APPEND_IMG_DONE = 'data-append-img-done',
  ATTR_NAME_APPEND_IMG = 'data-append-img';

  function extractImage(){
    forEach.call(document.getElementsByTagName('a'), function(el) {
      var href = el.href;
      if (href && href.match(/^https:\/\/.+(jpeg|jpg|gif|png)$/) && !el.hasAttribute(ATTR_NAME_APPEND_IMG_DONE)) {
        var img = document.createElement('img');
        img.setAttribute(ATTR_NAME_APPEND_IMG, 1);
        img.src = href;
        el.setAttribute(ATTR_NAME_APPEND_IMG_DONE, 1);
        el.parentNode.appendChild(img);
      }
    });
  }
  function onDomNodeInserted(evt) {
    var srcElement = evt.srcElement;
    if (srcElement.hasAttribute && srcElement.hasAttribute(ATTR_NAME_APPEND_IMG)) return;
    extractImage();
  }
  function main() {
    extractImage();
    window.addEventListener('DOMNodeInserted', onDomNodeInserted, false);
  }
  window.addEventListener('load', main, false);
})();

(´・ω・｀)