Didn't you try localStorage() to make dark mode persist?

• When the

  page loads, check the theme is set to dark. Then it applies the dark mode.

   `let trilho = document.getElementById('trilho');
   let body = document.querySelector('body');
  
   const theme = localStorage.getItem("theme");
   if (theme === "dark") {
       trilho.classList.add("dark");
       body.classList.add("dark");
   }
  

• Every time when the user toggles the button, check the body has dark class. If it does save it on the localStorage,

  trilho.addEventListener('click', () => { trilho.classList.toggle('dark'); body.classList.toggle('dark');

   if (body.classList.contains("dark")) {
       localStorage.setItem("theme", "dark");
   } else {
       localStorage.setItem("theme", "light");
   }
  

  });