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perf: swap writer's spread-with-deltaTime for Object.assign #81

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perf: swap writer's spread-with-deltaTime for Object.assign #81

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9 changes: 6 additions & 3 deletions src/chart/midi-writer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -257,7 +257,10 @@ function buildUnrecognizedTrack(events: MidiEvent[]): MidiEvent[] {
const out: MidiEvent[] = []
for (const e of events) {
const absTick = e.deltaTime
out.push({ ...e, deltaTime: absTick - prevTick })
// Object.assign is noticeably faster than {...e, …} spread on V8 — tsup
// transpiles the spread to __spreadProps(__spreadValues(...)) which
// iterates property descriptors.
out.push(Object.assign({}, e, { deltaTime: absTick - prevTick }) as MidiEvent)
prevTick = absTick
}
return out
Expand Down Expand Up @@ -539,7 +542,7 @@ function buildDrumTrack(
events.push({
tick: ev.deltaTime,
seq: unrecSeqBase + unrecSeq++,
event: { ...ev, deltaTime: 0 } as MidiEvent,
event: Object.assign({}, ev, { deltaTime: 0 }) as MidiEvent,
})
}
}
Expand Down Expand Up @@ -1002,7 +1005,7 @@ function buildFretTrack(
events.push({
tick: ev.deltaTime,
seq: unrecSeqBase + unrecSeq++,
event: { ...ev, deltaTime: 0 } as MidiEvent,
event: Object.assign({}, ev, { deltaTime: 0 }) as MidiEvent,
})
}
}
Expand Down