A spread copy is ~1.4× slower than `Object.assign`

Object.assign wins for shallow copies. The gap is 1.4× — a small price for the readability of spread.

Result

Run	spread copy	`Object.assign(, obj)`	Ratio
Run 1	0.863	0.565	1.53×
Run 2	0.755	0.598	1.26×
Run 3	0.818	0.636	1.29×

Median spread: spread copy CV 5.5% / `Object.assign(, obj)` CV 4.9% / Ratio CV 8.8% (computed from the 3 runs)

Conditions

200,000 shallow copies of a 10-key object.

Where this number does not apply

Unless you copy every frame inside a hot loop, this difference will not be perceptible.

Reproduce

cd bench
node --expose-gc micro-fixed.mjs --out ../data/run.json --samples 21

Run it three times on the same machine; if the spread of median stays under 10%, you should land on the same conclusion. If your numbers disagree, tell us and we will retract.