V8 internals for JS developers
summary
Shows that small, concrete V8 facts change choices: arrays have element kinds like packed SMI elements vs holey double elements, transitions only go downward, holes force prototype lookups and slow everything. Chrome moved to Ignition + Turbofan (Chrome 59+) and progressively folders in per-kind optimizations. Debug builds of d8 expose kinds via %DebugPrint. Preallocating new Array(9001) creates holes; pushing keeps arrays packed but triggers about sixteen reallocations from the initial 16-slot buffer.
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chapters (8)
- 0:00Start
- 2:03Array Indexes
- 8:47Bounce Check
- 13:00Fine and Find Index
- 20:01Array like Objects
- 21:10Arguments Object
- 21:57Arrays
- 24:30Recap
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