Make JavaScript Faster
summary
Argues JavaScript is the biggest bottleneck: JavaScript consumes twice as much CPU as loading layout and rendering combined, backed by HTTP Archive data across 1.3 million URLs. Gives concrete wins: measure real-user CPU with the User Timing Spec and Long Tasks API, move heavy work off the main thread, preload critical scripts with link rel=preload, prefer defer over async for many cases, and shrink payloads using code coverage. Quotes medians and tails: desktop 95th ≈3.6s (99th ≈8s), mobile 95th ≈9.8s (99th ≈19s).
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chapters (19)
- 0:00Introduction
- 1:35Knuth quote
- 2:52HTTP Archive
- 3:55Performance Metrics
- 5:50Ageism
- 7:33Ie7 2007
- 8:52IE8 2008
- 10:51Browser Scope
- 11:49Preloader
- 13:59Async
- 14:37New York Times
- 15:24Async Adoption
- 16:50Why Do Scripts Jump in May
- 18:12Linkrel Preload
- 21:37CPU
- 27:23Third Party
- 28:41Gzip
- 31:32Code Coverage
- 33:01Conclusion
