Scala.js Semantics - and how they support performance and JavaScript interop

on YouTube ↗42m

" summary

Scala.js defines precise runtime rules that make Scala values behave like JavaScript where needed and preserve Scala semantics elsewhere, with a three-mode safety model (full checks in dev, unchecked fast mode in prod). Integers use real 32-bit encoding (a |0 trick) so tight math is fast and boxing disappears, longs live in a userland library and stay slow, and a whole-program optimizer eliminates lambdas and allocations (foldLeft becomes a while loop), achieving near-handwritten JS speeds on Octane; Closure sometimes regresses.

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" chapters (6)

1. 0:00Start
2. 7:48Primitive Data Types
3. 15:16Define Behaviors
4. 20:19Javascript Interop
5. 24:12Runtime Semantics
6. 28:06Primitive Types

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