はてなブログの各記事に最終更新日を追加するスクリプト

add_lastmodDate_into_hatenablog.js

(function(){
/*
- args: lastmod: str
*/
function addLastmod(lastmod){
  /* ここでlastmodを追加 */
  var time = document.createElement("time");
  time.setAttribute("itemprop", "dateModified");
  time.setAttribute("title", lastmod);
  time.setAttribute("datetime", lastmod);
  time.innerText=lastmod;
  var span = document.createElement("span");
  span.innerHTML = "(LastModified: " + time.outerHTML + ")";
  var date_elements = document.querySelectorAll("div.date")
  Array.prototype.map.call(date_elements, function(e){e.appendChild(span);});
}

var blog_uri = document.querySelector("[data-blog-uri]").getAttribute("data-blog-uri");
var sitemap_url = blog_uri + "sitemap.xml";
var article_url = document.querySelector('[property="og:url"]').getAttribute("content");

function fetch2str(res) {
  return res.text();
}

function str2dom(str) {
  var parser = new DOMParser();
  var dom = parser.parseFromString(str, 'text/xml');
  return dom;
}

/*
return : Promise([URL1, URL2, ...])
*/
function getSitemapURLArrayPromiseFromSitemapXML() {
  return fetch(sitemap_url)
    .then(fetch2str)
    .then(str2dom)
    .then(function(dom) {
      return Array.prototype.map.call(dom.querySelectorAll("sitemap"), function(e) {
        return e.querySelector("loc").innerHTML
      });
    });
}

/*
- return Promise([""<xml >?page=1...</xml>", "<xml >?page=2...</xml>", ...])
*/
function getXMLStrArrayPromiseFromAllSitemapURL(URL_array) {
  return Promise.all(URL_array.map(function(e) {
    return fetch(e).then(fetch2str);
  }));
}

/*
return Promise(url_element in DOMParser)
*/
function find_urlElementMatchedAtriclePromiseFromXMLStrArray(xml_str_arr) {
  var parser = new DOMParser();
  var find_url_e = undefined;
  for (var xml_str of xml_str_arr) {
    var dom = parser.parseFromString(xml_str, 'text/xml');
    var url_elements = dom.querySelectorAll("url");
    find_url_e = Array.prototype.find.call(url_elements, function(e, idx, arr) {
      return e.querySelector("loc").innerHTML === article_url;
    });
    if (find_url_e) break;
  }
  return find_url_e;
}

function getLastmodFrom_urlElement(url_element){
  return url_element.querySelector("lastmod").innerHTML;
}

try{
getSitemapURLArrayPromiseFromSitemapXML()
  .then(getXMLStrArrayPromiseFromAllSitemapURL)
  .then(find_urlElementMatchedAtriclePromiseFromXMLStrArray)
  .then(getLastmodFrom_urlElement)
  .then(addLastmod);
}catch(e){
  console.log(e);
}
}());