Add cool effect when trnsitionning from light to dark mode using css and view transitions

copied from @jhey on twitter

[!NOTE]
This assumes you've already have your dark light mode setup with some sort of function to update your theme

1. Add the css

  /* Angled */
  [data-style='angled']::view-transition-old(root) {
    animation: none;
    z-index: -1;
  }

  [data-style='angled']::view-transition-new(root) {
    animation: unclip 1s;
    clip-path: polygon(-100vmax 100%, 100% 100%, 100% -100vmax);
  }

  @keyframes unclip {
    0% {
      clip-path: polygon(100% 100%, 100% 100%, 100% 100%);
    }
  }

1. ensure data-style="angled" attribute is set on the root element in SPA react we use a useEffect hook

  useEffect(() => {
    // set the data-style attribute
    document.documentElement.dataset.style = "angled";
  }, []);

in SSR it can be set directly in the html tag

1. wrap your theme change function in a documnet.startViewTransition to start the view transition

  function transitionColors() {
    if (typeof window !== "undefined") {
      document.startViewTransition(() => {
        const newTheme = theme  === "light" ? "dark" : "light";
        document.documentElement.dataset.theme = newTheme;
        updateTheme(newTheme);
      });
    }
  }

more transition styles can be added by including the corresponding css file and adding the correct data-style attribute

      
          (document.documentElement.dataset.style = e.target.value)
        }
      >
        DefaultVerticalWipeAngledFlipSlides

react example

If you like this type of css tricks consider following jhey