Friday, May 8, 2020 [Tweets] [Favorites]

Rewriting Facebook.com

Ashley Watkins and Royi Hagigi (via Hacker News):

A complete rewrite is extremely rare, but in this case, since so much has changed on the web over the course of the past decade, we knew it was the only way we’d be able to achieve our goals for performance and sustainable future growth. Today, we’re sharing the lessons we’ve learned while rearchitecting Facebook.com, using React (a declarative JavaScript library for building user interfaces) and Relay (a GraphQL client for React).

[…]

On our old site, we were loading more than 400 KB of compressed CSS (2 MB uncompressed) when loading the homepage, but only 10 percent of that was actually used for the initial render. We didn’t start out with that much CSS; it just grew over time and rarely decreased. This happened in part because every new feature meant adding new CSS.

[…]

By using rems, we can respect user-specified defaults and are able to provide controls for customizing font size without requiring changes to the stylesheet. Designs, however, are usually created using CSS pixel values. Manually converting to rems adds engineering overhead and the potential for bugs, so we have our build tool do this conversion for us.

[…]

To prevent flickering as icons come in after the rest of the content, we inline SVGs into the HTML using React rather than passing SVG files to <img> tags. Because these SVGs are now effectively JavaScript, they can be bundled and delivered together with their surrounding components for a clean one-pass render.

Previously:

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