css-modules VS JSS

One aspect of CSS modules that I truly appreciate is its ability to compress class names into very short hashes. This feature allows me to keep my CSS selectors as long and descriptive as needed, while still compressing them into concise three or four character hashes. It aligns with my rule for CSS: selectors should be written for human readability, but compressed for machine efficiency.

Use methodologies such as BEM, and technologies including CSS modules, CSS-in-JS, and Shadow DOM to isolate the styles of each micro-application and prevent conflicts, thus ensuring reliable encapsulation and modularity.

For many years, Culture Amp took the second option, and distributed shared components without compiled CSS. This meant that every app that consumed shared components needed to include the necessary CSS build tooling – at that time CSS Modules and node-sass – with a compatible version and configuration. This was relatively easy to set up, but over time proved difficult to maintain. When node-sass was deprecated in favour of (the much faster but slightly incompatible) Dart Sass, this demanded a difficult lock-step migration across all those codebases, which we have yet to achieve. And as new applications have switched to Tailwind for their own styles, they've had to continue to maintain those old build tools in parallel for the shared components' styles.

So CSS modules are a form of 3rd-party CSS-in-JS, where what you import are the class names, which are then usually obfuscated etc at compile time, and all the actual style declarations are (usually) compiled into a single css file or tag as part of the bundling process. You can read the og docs on'em here, and you've probably seen'em used in React like:

import styles from "./styles.css";

function Example(){
    return (
        

            Hello
        
    );
}

They predate the ability to import non-js files in vanilla by a good while, and rely on the compile process to translate your .css files into .js files that can be imported using whichever loader you use in your bundler.

Import assertions are a vanilla way to import non-js files by telling the browser how to import them; assert { type: "css" } says to treat the file as CSS and create a CSSStyleSheet, assert { type: "json" } says to treat the file as JSON and create a JSON object - and hopefully assert { type: "html" } will hopefully arrive soon and create a #document-fragment or something similar.

Hope that clears it up!

Extensions of CSS: for example, Sass, Less, Tailwind, CSS Modules, to make stuff look a certain way on your own.

The components are styled with CSS modules. When building the library, these styles will get transformed to normal CSS style sheets. This means that the consuming application will not even be required to support CSS modules. (In the future I want to extend this tutorial to use vanilla-extract instead.)

NextJS comes with built-in support for CSS Modules which allows you to scope your styles locally in individual components without worrying about name collisions or messing up other parts of the codebase.

CSS modules are not to be confused with mixins, as they serve the opposite purpose. While mixins are components or functions to be reused globally, modules are style sheets with a local scope used in a similar way as styled components in React.

CSS Modules CSS Modules is a pre-processing step: by default, styles are scoped locally to the current component, and the transpiler ensures no conflicts.

Most websites those days are SPA applications that render on the front-side. There is also this trend of CSS in JavaScript also knowns as JSS that is debatable (makes everything overcomplicated), but in some specific cases, can be justified and very useful.

> why tf aren't we using JS for styling already

People are and have been for quite a while

https://cssinjs.org/

JSS

It is possible. At its most simple, you could just modify the style property on every element. That's not generally considered best practice, but there are a number of "CSS-in-JS" libraries which streamline the process. The typically generate dynamic CSS classes and apply them to your elements. A big one is JSS.

import React, { useState, useEffect } from "react"; import Amplify, { API, graphqlOperation } from "aws-amplify"; import { createBlog } from "./graphql/mutations"; import { listBlogs } from "./graphql/queries"; import awsExports from "./aws-exports"; import { ListBlogsQuery } from "./API"; Amplify.configure(awsExports); const initialState = { name: "", body: "" }; const App = () => { const [formState, setFormState] = useState(initialState); const [blogs, setBlogs] = useState(); useEffect(() => { fetchBlogs() }, []); const handleInputChange = (event: React.ChangeEvent) => { setFormState({ ...formState, [event.target.name]: event.target.value }); }; const fetchBlogs = async () => { try { const blogData = (await API.graphql(graphqlOperation(listBlogs))) as { data: ListBlogsQuery } setBlogs(blogData.data); } catch (err) { console.log("Error fetching blogs" + err); } }; const addBlog = async () => { try { if (!formState.name || !formState.body) return; const blog = { ...formState }; if (blogs) { await API.graphql(graphqlOperation(createBlog, { input: blog })); await fetchBlogs(); setFormState(initialState); } } catch (err) { console.log("error creating blog: ", err); } }; return (

Amplify Todos

Create Blog {blogs && blogs?.listBlogs?.items?.map((blog, index) => { return (

{blog?.name}

{blog?.body}

); })}

); }; const styles = { container: { width: 400, margin: "0 auto", display: "flex", //real weird issue: https://github.com/cssinjs/jss/issues/1344 flexDirection: "column" as "column", justifyContent: "center", padding: 20, }, todo: { marginBottom: 15 }, input: { border: "none", backgroundColor: "#ddd", marginBottom: 10, padding: 8, fontSize: 18, }, todoName: { fontSize: 20, fontWeight: "bold" }, todoDescription: { marginBottom: 0 }, button: { backgroundColor: "black", color: "white", outline: "none", fontSize: 18, padding: "12px 0px", }, }; export default App;

Material UI v5 brought some amazing updates, but switching from JSS to Emotion had an arguably nasty side-effect: it was no longer as straightforward to group your component styles in classes. Fortunately, a fantastic library emerged that allowed developers to not only reduce the extreme pain from migrating all their classes from v4's makeStyles to emotion, but to also to continue to writing classes in practically the same syntax, with wonderful TS type-safety. This library was tss-react, and it was one of my favorite open source discoveries of 2021.

I started writing a long response, but I want to add that a simple CRA + JSS + TS (named exports only) stack solves or abstracts away most of these issues.

JSS