A Journey toward better style

Acknowledgment

• I would like to thank Nathan Marks for the awesome work is has done addressing the styling issues.
• I would like to thank Pete Hunt for his inspiring talk on reusable components.
• I would like to thank the following oranizations for giving me the opportunity to share this topic:
• Paris.js
• ReactJS-Paris

Date

• 2016-10-27
• 2017-01-26

Online version

• show
• presenter

CSS-in-JS comparison

We started looking for the best styling solution available. Nathan Marks built a custom solution for the needs of Material-UI: stylishly. Ultimately we reverted. We think that it's much better to rely on the community. Still, that was a very valuable experimentation.

Regarding the community, looking at the MicheleBertoli's repository. You can tell that there is a lot a solution available.

What's the best one for our needs?

For the sake of this presentation, I have selected 5 libraries that I think have taken valuable tradeoffs. I'm gonna give my point of view in the rest of this section. The information given are biased by my understanding of the reality.

• CSS modules

  • Singularity: Extended CSS DSL. Generate style at built time.
  • Motivation: Having some isolated and composable module of CSS. Stay as close as possible to the CSS ecosystem.

• Aphrodite

  • Singularity: Per rule style usage and injection.
  • Motivation: Khan Academy was looking for a better way to style components with an existing code base. E.g. usage of !important.

• styled-components

  • Singularity: Uses post-CSS at runtime.
  • Motivation: ? My best guess is, leveraging JS power while still using the CSS syntax.

• JSS

  • Singularity: Has a low-level API.
  • Motivation: ? I have no clue. I should be asking @nathanmarks.

• Fela

  • Singularity: Has a functional API.
  • Motivation: ? Could be inspired by posts like Functional Programming, CSS, and your sanity.

Interesting dimensions

We can't compare anything without some dimensions. But having too much of them add noise.

:warning: Be aware that horse transportation is better than cars when following biased dimensions. I have sorted them by importance.

• The API.
• Is it taking full advantage of JavaScript? JavaScript is a much more powerful language than CSS. When using it, you no longer have to worry about CSS linter, CSS syntax, CSS pre-processor
• Is the API low or high level? The theming requirement is quite high for Material-UI. The much freedom we have, the better.
• Is the API declarative? The more declarative we are, the better.
• Time to first paint. We have a legacy of poor performance with our inline-style implementation (lack of caching). Reducing the delay between an interaction and something on the screen is quite critical for us. I have run a simple benchmark on a modified version of CSS-in-JS There is quite some factor than can make a difference. I have noticed a factor x2 of difference between the fastest solution (CSS modules) and the slowest one (styled-components).
• Is the style pre-processed at runtime of build time?
• Is the style injected as class names used or upfront during the bootstrap?
• How are the classNames generated? E.g. computing a hash of the rule object could be expensive.
• Library size. Users of Material-UI could be using a single component out of the available ones. E.g. the <DatePicker />. We want to minimize the entry price of using a single component.
• Server Rendering. Server side rendering a page drastically improve perceived performance for a user first visit (for repetitive one, Service Worker are even more efficient). Material-UI can't be taken seriously without a strong answer to this point.
• Can requests be parallelized? I.e, not using a singleton, that's also bad for security.
• Is the API allowing streaming the response?
• Unbiased. The less coupled with a solution we are the better. We also want to make sure the solution we are going to use reach a broad audience. E.g. LESS is used by the Angular and React community. That's increasing odds of success.
• Are we coupled to React?
• Are we coupled to Webpack?
• Debug. Users of Material-UI were complaining that the debugging experience was poor with inline-style. Browser dev tool handles much better the CSS. Still, the styling solution can impact it.
• Are the classNames readable in dev mode?
• Are the classNames injected into a single style element or multiple?
• CSS output size. That last dimension is less interesting. I was just curious.

Results

• ++ awesome
• + great
• o enough
• - not great
• -- no

Going forward

Material-UI has chosen JSS. It's addressing our unique needs. Your needs are most likely different. It could be better for you to use a another solution. Be sure you make an informed choice :bulb:.

The compared libraries are going to improve. My comparison might not worth anything one year from now.