july-07.md

July 07 (discuss)

Attendees

• Ben (React)
• Christopher (React)
• Dan (React)
• Keyan (React, intern)
• Paul (React)
• Sebastian (React)
• Tom (React)

Fragments

• We don’t currently allow returning multiple elements from render() method.
• This has been a long requested feature in the community.
• We generally agree that it should be implemented but we found it to be hard with our existing architecture.

Existing Solutions

• There exists a fork that implements fragments but we don’t want to take this implementation.
• It introduces them only for React DOM which would make React features inconsistent across renderers.
• It also introduces some complexity we would like to avoid because we might start breaking other things with it.

Our Plans

• Fiber supports fragments but it’s far from done.
• We will include work on fragments in our plan for the second half of 2016.
• Since we want this feature anyway, we can implement it in existing reconciler independently of Fiber.

Build Size

• We think that React provides good value for its build size (~45kB min+gzip).
• However we understand everybody has different constraints, especially with small apps.
• We intend to be more mindful of the build size to avoid accidental regressions.

Rollup

• Keyan is investigating using Rollup for our UMD builds. (#7178)
• After #7178 is merged, the minified post-gzip size will reduce by 14%. (46kB → 39kB)
• For now, we will use a hack to transpile CommonJS to ES Modules so Rollup understands them.
• Longer term, we’d like to use ES Modules in the source but Facebook internal bundlers don’t understand them yet.

Event System

• Dan asked why the event system is so large.
• It accounts for a noticeable chunk of React build size.
• Looking at other “React-like” libraries, no one has an event system like ours. Why?

Why We Need It

• The intention was to normalize events with weird behavior like mouseenter or focus across browsers.
• This lets component authors not worry about inconsistencies with bubbling and input events, making ecosystem better.
• The React Native gesture handling system is also built around it.
• The browsers have improved, so we will keep re-evaluating it once in a while, but for now we find it useful.

What We Can Improve

• It is overabstracted, and we can simplify code by baking support for some “plugins” right into it.
• There is some code duplication we can reduce in the event whitelist.
• Some weird patterns like keyOf() exist to be compatible with GCC. Perhaps we could find another way to fix this?

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Please feel free to discuss these notes in the corresponding pull request.