dark-mode.user.js

// ==UserScript==
// @name         Dark Mode
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  pub med dark mode
// @author       Josh Parker
// @match        https://www.ncbi.nlm.nih.gov/pmc/
// @match        https://www.ncbi.nlm.nih.gov/pmc/*
// @match        https://pubmed.ncbi.nlm.nih.gov/*
// @icon         https://www.google.com/s2/favicons?domain=nih.gov
// @grant        none
// ==/UserScript==

(function darkMode() {
 const addRule = (rule) => document.styleSheets[0].insertRule(rule);

 const maincontentSelectors = [
  'html > body',
  'html > body div.article-page#article-page',
  '#maincontent #mc',
  '#maincontent #mc div.table-wrap',
  'body#ui-ncbiexternallink-3',
  '#ui-ncbiexternallink-3 > .grid > .col',
  '.bottom #footer',
  '.bottom .contact_info',
  '#ajax-portlets div',
  '#ajax-portlets div .one_line_source',
  '#ajax-portlets div.portlet ul > li.two_line .one_line_source',
  '#ajax-portlets div.portlet ul > li.two_line .source',
  '#ajax-portlets div.portlet ul li.expanded.highlight',
  '.page .content #rightcolumn',
  '.page > .content > .container > .col',
 ];

 addRule(`${maincontentSelectors.join(', ')} { color: white; background-color: black; }`);

 const boxSelectors = [
  '#maincontent #mc #pmclinksbox',
  '.page .top .ncbi-alerts .ncbi-alert__shutdown-outer',
  '#maincontent #mc div.iconblock',
  '#maincontent #mc div.iconblock .icnblk_cntnt',
 ];

 addRule(`${boxSelectors.join(', ')} { color: white; background-color: #990; }`);
 addRule(`${boxSelectors.map((bs) => `${bs} a`).join(', ')} { color: #CFF; }`);

 const dropdownSelectors = [
  '#maincontent #mc .ui-ncbilinksmenu',
  '#maincontent #mc .ui-ncbilinksmenu .oneLevel li a',
  '#maincontent #mc .ui-ncbilinksmenu .ui-ncbibasicmenu li a',
 ];

 addRule(`${dropdownSelectors.join(', ')} { background: #222; box-shadow: 0 0 1em 1em #666; }`);

 const miscRules = [
  '.bottom #footer a[href], .page .content a[href] { color: #BBF; }',
  'div.footer#footer { background: black; }',
  '#footer ul > li > h3, #maincontent #mc h3, #maincontent #mc h4, #maincontent #mc h2, #ajax-portlets .portlet h3 { color: #FDB; }',
  '#maincontent #mc h1 { color: white; }',
  '#maincontent #mc div.table-wrap { border: 2px solid white; }',
  '#ajax-portlets div.pmc_para_cit { border: none; border-top: 1px solid white; }',
  '#ajax-portlets .portlet { border-top: .4em solid #97b0c8; }',
  '.page .content #rightcolumn .share-buttons a, .page .content #rightcolumn .format-menu ul li.selected { color: #bbb; }',
  '.page .content .ncbi-alerts .pmc-labs-ad-outer { background-color: #055; }',
 ];

 miscRules.forEach((rule) => addRule(rule));
}());