Simple Dark Theme Bookmarklet for web pages

darkthemeswitcher-inline.js

javascript:(d=>{var css=`:root{background-color:#fefefe;filter:invert(100%)}*{background-color:inherit}img:not([src*=".svg"]),video{filter: invert(100%)}`,style,id="dark-theme-snippet",ee=d.getElementById(id);if(null!=ee)ee.parentNode.removeChild(ee);else {style = d.createElement('style');style.type="text/css";style.id=id;if(style.styleSheet)style.styleSheet.cssText=css;else style.appendChild(d.createTextNode(css));(d.head||d.querySelector('head')).appendChild(style)}})(document)

darkthemeswitcher.js

javascript:
(d=>{
  var css = `
        :root{
          background-color: #fefefe;
          filter: invert(100%)
        }
        * {
          background-color: inherit
        }
        img:not([src*=".svg"]), video{
          filter: invert(100%)
        }
  `,
  style,
  id="dark-theme-snippet",
  ee = d.getElementById(id);
  if (null != ee) ee.parentNode.removeChild(ee);
  else {
    style = d.createElement('style');
    style.type = "text/css";
    style.id = id;
    if (style.styleSheet) style.styleSheet.cssText = css;
    else style.appendChild(d.createTextNode(css));
    (d.head||d.querySelector('head')).appendChild(style);
  }
})(document)

I've forked it into a version that does not ruin iframes (like embedded YouTube) and images that use background-image= instead of <img.