Mehul Kar

06 Mar, 2017

Switching to Functional CSS


I just switched over to tachyons on one of my projects. Tachyons is a functional CSS library. It provides you with a ton of pre-written classes, each of which do only one thing and are organized in easily guessable patterned names. For example, the class .mb1 means “apply a margin-bottom rule of scale 1. The scale 1 is relative and I didn’t really care to learn what the actual values were as long as they were consistent.

Converting to tachyons was a pretty fun process, so I’d like to document some key learnings.

Key learnings:

  • I was able to throw away most of the rules I had written for margins, padding, borders, colors, font sizes and weights. There were surprisingly a lot of these that were inconsistent and sloppily organized.
  • Applying a bunch of classes to a single element feels almost like inline styles, except you get relative scales and shorthand syntax. For example, <span class='pa3 mb4 f1 red'>text</span> applies a:
    • padding on all sides of relative scale 3
    • margin-bottom of relative scale 4
    • font-size of relative scale 1 (the biggest)
    • color of red
  • Not being able to create a .special-class that encapsulates styles, like I would be able to with more of a component approach, forced me to look for template abstractions and partials, which ended up being a really good for design consistency.
  • I probably introduced some inconsistencies because of typos or by accidentally using pv2 instead of pv3 (pv is shorthand for both padding-top and padding-bottom), but these inconsistencies were a thousand times easier to debug than delving into CSS.
  • I had to add a couple colors in the same style as the ones provided by the library to get my brand colors. I just added the rules I needed, not ALL possible uses for the color.
  • I was able to completely get rid of bootstrap library and a bootstrap theme. and reduce my CSS down from almost 1MB to 200kb to achieve a near identical look and feel on the website.
  • Since this is a Rails app, I write my styles in SCSS. In development mode, these styles are pre-compiled on page load if any rules change. Pre-compilation takes longer the more files of SCSS you have. I had a bunch of these files (one for each "component”), but since I was able to delete a lot of my styles, my development flow became much quicker (from about ~4 seconds to load to <1 second to load a page after changing a custom CSS rule).
  • There was a little bit of a learning curve, but I was able to learn the patterns of class names pretty quickly. I also downloaded the source for the tachyons website and docs, and did a global search in it in my text editor to find the class names that corresponded to certain rules. This worked pretty well since I was working on my migration offline on a plane.

I feel pretty confident that a new contributor would be able to pick up on these patterns and apply the same styles much more quickly than if they were to try to look through my code.

Another thing I noticed is that writing CSS in a component approach requires me to be very disciplined about doing things The Right Way™, and constantly looking for abstractions. With this functional approach, I was able to throw a bunch of classes at an element and not only did it do what I wanted it to do, it was also already at a very low level of entropy. I think optimizing for laziness is a good thing.

Want to talk about this blag? Email me or send me a toot @mehulkar!