hatecomputers.club/static/js/util/setThemeBeforeRender.js

const preferredMode = window.matchMedia("(prefers-color-scheme: dark)").matches
  ? "DARK"
  : "LIGHT";
localStorage.setItem("theme", localStorage.getItem("theme") || preferredMode);

// sets theme before rendering & jquery loaded to prevent flashing of uninitialized theme
// (ugly white background)
document.documentElement.setAttribute("data-theme", preferredMode);