google_scholar_auto_gateway.user.js

// ==UserScript==
// @name     Google_Scholar_on_UTokyo_gateway
// @version  2
// @include  https://scholar.google*
// @grant    none
// @require  https://code.jquery.com/jquery-3.5.0.slim.min.js
// This software is released under the MIT License, see LICENSE.
// ==/UserScript==

function get_gateway_url(url){
  const url_obj = new URL(url);
  if(url.match('arxiv')){
    return url;
  } else {
    return 'https://' + url_obj.hostname.replace(/\./g, '-') + '.utokyo.idm.oclc.org' + url_obj.pathname + url_obj.search;
  }
}

function article_page_block(block){
    if($(block).find("span.gs_ctc").length == 1){ //[PDF] or [HTML]
      return false;
    }else{
      return true;
    }
}

(function() {
  const re_url = new RegExp('^(https?|ftp):\/\/');
  const article_block = $('#gs_res_ccl_mid .gs_ri');
  article_block.each((i, e) => {
    if(article_page_block(e)){
      const journal_links = $(e).find("a").filter((i, link) => {
        const href = link.href
        return href.match(re_url) && (!href.match('google')) && link.hasAttribute("id");
      });
      journal_links.each((i, link) => {
        link.href = get_gateway_url(link.href);
      });
    }
  });
})();