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All things Mike .

More on modular CSS

I’m always on the lookout for thought-provoking discussion about CSS, since I find it so rare. Smashing Magazine can occasionally turn up quality information about CSS, as they did recently in a guest piece that described the nose-to-tail rebuild of the London Times’ website. An interesting read overall, the part that stood out most to me detailed their approach to CSS. They anticipated pain around HTML view re-use and re-composition (into various layouts), and sought to structure their CSS accordingly. I applaud their efforts (despite dropping the goal of semantic naming, which would seriously concern me), and noticed that it resembled an approach I had taken early in Blocvox’s development. I weighed in to share my experiences, and wanted to reproduce it here as a follow up to techniques described in my recent post about the motive for modular CSS.



I started with the same use of long/multipart class names, and although it is performant, I found it a bit cumbersome to develop with. In my approach, I strictly adhered to representing each level of structure in the class name, so a link in the headline would have the class name ‘.apple_headline_link’. This made nesting or un-nesting elements require a lot of tedious class renaming, making rapid experimentation very burdensome.

Instead, I switched to a convention that relies on the child combinator. E.g.,

.apple { /* rules */ }
.apple > .-headline { /* rules */ }
.apple > .-headline > .-link { /* rules */ }
.apple > .-subHead { /* rules */ }
.apple > .-subHead > .-link { /* rules, can differ from header link */ }
.apple > .-body { /* rules */ }

The benefit of this comes when using a CSS preprocessor. I use Stylus, since I use Node.js for build tooling.

.apple
  // rules
  > .-headline
    // rules
    > .-link
      // rules
  > .-subHead
    // rules
    > .-link
      // rules
  > .-body
    // rules
  &._green
    background-color: green
    > .-headline
      color: white

Now moving elements around only requires adding/removing a selector and indenting/un-indenting a bunch of declaration blocks. Performance is still good, but theoretically not as good as single class selectors.

A necessary part of this approach is that sub-elements have class names beginning with a dash, while root elements do not. A corollary is that all class names beginning with a dash are only used in selector groups scoped to a root class. With this convention, sub-elements are like private variables in OOP, with no meaning in the global class namespace.

I also use “flags” (e.g. “_green”, using an underscore prefix naming convention), which are analagous to a public boolean property in the OO world. Consumers are free to “set” any supported flag on a module’s root element.

Follow me on Twitter for the latest updates, and make sure to check out my community opinion startup, Blocvox.



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