> The tragedy of commons here is that you _could_ conceivably just slap a class at the root of your React tree to implement dark mode, but if one is using something like styled-components, there's a good chance that the library will get in the way of the style cascading semantics that come for free w/ the browser.
A decent dark mode is going to take a lot than a class at the root in any case (a class at the root makes a good toggle, sure, but you have to do all the styling if particular elements that that toggle applies.)
If you have handrolled CSS for your light theme and want to add a dark theme toggle, hand rolling CSS for it and toggling with a class at the root is pretty idiomatic React.
If you've chosen a styling/theming library to solve other problems, or incidentally to doing so as might have happened if you chose Material-UI, then, sure, a class at the root might not work well, and/or you might have a much easier solution (not easier than the class at root but easier than the rest of the work of implementing a dark theme) for adding a toggleable dark theme. Like in Material-UI, where you just tell the theming solution you’d like the computed dark version of a theme.
A decent dark mode is going to take a lot than a class at the root in any case (a class at the root makes a good toggle, sure, but you have to do all the styling if particular elements that that toggle applies.)
If you have handrolled CSS for your light theme and want to add a dark theme toggle, hand rolling CSS for it and toggling with a class at the root is pretty idiomatic React.
If you've chosen a styling/theming library to solve other problems, or incidentally to doing so as might have happened if you chose Material-UI, then, sure, a class at the root might not work well, and/or you might have a much easier solution (not easier than the class at root but easier than the rest of the work of implementing a dark theme) for adding a toggleable dark theme. Like in Material-UI, where you just tell the theming solution you’d like the computed dark version of a theme.