rowid,title,contents,year,author,author_slug,published,url,topic 216,Styling Components - Typed CSS With Stylable,"There’s been a lot of debate recently about how best to style components for web apps so that styles don’t accidentally ‘leak’ out of the component they’re meant for, or clash with other styles on the page. Elaborate CSS conventions have sprung up, such as OOCSS, SMACSS, BEM, ITCSS, and ECSS. These work well, but they are methodologies, and require everyone in the team to know them and follow them, which can be a difficult undertaking across large or distributed teams. Others just give up on CSS and put all their styles in JavaScript. Now, I’m not bashing JS, especially so close to its 22nd birthday, but CSS-in-JS has problems of its own. Browsers have 20 years experience in optimising their CSS engines, so JavaScript won’t be as fast as using real CSS, and in any case, this requires waiting for JS to download, parse, execute then render the styles. There’s another problem with CSS-in-JS, too. Since Responsive Web Design hit the streets, most designers no longer make comps in Photoshop or its equivalents; instead, they write CSS. Why hire an expensive design professional and require them to learn a new way of doing their job? A recent thread on Twitter asked “What’s your biggest gripe with CSS-in-JS?”, and the replies were illuminating: “Always having to remember to camelCase properties then spending 10min pulling hair out when you do forget”, “the cryptic domain-specific languages that each of the frameworks do just ever so slightly differently”, “When I test look and feel in browser, then I copy paste from inspector, only to have to re-write it as a JSON object”, “Lack of linting, autocomplete, and css plug-ins for colors/ incrementing/ etc”. If you’re a developer, and you’re still unconvinced, I challenge you to let designers change the font in your IDE to Zapf Chancery and choose a new colour scheme, simply because they like it better. Does that sound like fun? Will that boost your productivity? Thought not. Some chums at Wix Engineering and I wanted to see if we could square this circle. Wix-hosted sites have always used CSS-in-JS (the concept isn’t new; it was in Netscape 4!) but that was causing performance problems. Could we somehow devise a method of extending CSS (like SASS and LESS do) that gives us styles that are guaranteed not to leak or clash, that is compatible with code editors’ autocompletion, and which could be pre-processed at build time to valid, cross-browser, static CSS? After a few months and a few proofs of concept later (drumroll), yes – we could! We call it Stylable. Introducing Stylable Stylable is a CSS pre-processor, like SASS or LESS. It uses CSS syntax so all your development tools will work. At build time, the Stylable CSS extensions are transpiled to flat, valid, cross-browser vanilla CSS for maximum performance. There’s quite a bit to it, and this is a short article, so let’s look at the basic concepts. Components all the way down Stylable is designed for component-based systems. Imagine you have a Gallery component. Within that, there is a Navigation component (for example, containing a ‘next’, ‘previous’, ‘show all thumbnails’, and ‘show all albums’ controls), and within that there are NavButton components. Each component is discrete, used elsewhere in the system in different contexts, perhaps maintained by different team members or even different organisations — you can use Stylable to add a typed interface to non-Stylable component libraries, as well as using it to build an app from scratch. Firstly, Stylable will automatically namespace styles so they only apply inside that component, by rewriting them at build time with a unique (but human-readable) prefix. So, for example,
might be re-written as
. So far, so BEM-like (albeit without the headache of remembering a convention). But what else can it do? Custom pseudo-elements An important feature of Stylable is the ability to reach into a component and style it from the outside, without having to know about its internal structure. Let’s see the guts of a simple JSX button component in the file button.jsx: render () { return ( ); } (Note:className is the JSX way of setting a class on an element; this example uses React, but Stylable itself is framework-agnostic.) I style it using a Stylable stylesheet (the .st.css suffix tells the preprocessor to process this file): /* button.st.css */ /* note that the root class is automatically placed on the root HTML element by Stylable React integration */ .root { background: #b0e0e6; } .icon { display: block; height: 2em; background-image: url('./assets/btnIcon.svg'); } .label { font-size: 1.2em; color: rgba(81, 12, 68, 1.0); } Note that Stylable allows all the CSS that you know and love to be included. As Drew Powers wrote in his review: with Stylable, you get CSS, and every part of CSS. This seems like a “duh” observation, but this is significant if you’ve ever battled with a CSS-in-JS framework over a lost or “hacky” implementation of a basic CSS feature. I can import my Button component into another component - this time, panel.jsx: /* panel.jsx */ import * as React from 'react'; import {properties, stylable} from 'wix-react-tools'; import {Button} from '../button'; import style from './panel.st.css'; export const Panel = stylable(style)(() => (
)); In panel.st.css: /* panel.st.css */ :import { -st-from: './button.st.css'; -st-default: Button; } /* cancelBtn is of type Button */ .cancelBtn { -st-extends: Button; background: cornflowerblue; } /* targets the label of