⚡ Bolt: [performance improvement]#225
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Refactors `groupTalksByTrack` to avoid spreading arrays inside `.reduce`. Using `.push` with `.forEach` reduces amortized memory allocations from O(N^2) to O(N). Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
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📝 WalkthroughWalkthroughThe ChangesGrouping implementation refactoring
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Possibly related PRs
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Code Review
This pull request refactors the groupTalksByTrack function to improve performance by replacing an inefficient reduce operation with a direct Map implementation. Feedback suggests further optimizing the iteration by using a for...of loop instead of forEach to avoid function call overhead and improve idiomaticity.
| talks.forEach((talk) => { | ||
| const track = getTrackFromTalk(talk); | ||
| return { | ||
| ...acc, | ||
| [track]: [...(acc[track] || []), talk], | ||
| }; | ||
| }, {}); | ||
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| return new Map(Object.entries(groupedObj)); | ||
| const existing = map.get(track); | ||
| if (!existing) { | ||
| map.set(track, [talk]); | ||
| } else { | ||
| existing.push(talk); | ||
| } | ||
| }); |
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While the refactor to O(N) is a significant improvement, using a for...of loop is generally more performant and idiomatic in TypeScript for loops with side effects (like mutating a Map) compared to .forEach. It avoids the overhead of a function call per iteration. Additionally, the logic can be slightly simplified by checking for the existing group and pushing to it directly.
As a modern alternative, if your environment supports ES2024, you could use Map.groupBy(talks, getTrackFromTalk), which is specifically designed for this purpose.
| talks.forEach((talk) => { | |
| const track = getTrackFromTalk(talk); | |
| return { | |
| ...acc, | |
| [track]: [...(acc[track] || []), talk], | |
| }; | |
| }, {}); | |
| return new Map(Object.entries(groupedObj)); | |
| const existing = map.get(track); | |
| if (!existing) { | |
| map.set(track, [talk]); | |
| } else { | |
| existing.push(talk); | |
| } | |
| }); | |
| for (const talk of talks) { | |
| const track = getTrackFromTalk(talk); | |
| const group = map.get(track); | |
| if (group) { | |
| group.push(talk); | |
| } else { | |
| map.set(track, [talk]); | |
| } | |
| } |
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💡 What
Refactored
groupTalksByTrackinhooks/useTalks.tsto replace a.reduce()loop containing array and object spread operators (...acc,[...acc[track], talk]) with aMappopulated via a.forEachloop and local mutation (.set(),.push()).🎯 Why
When grouping large numbers of talks by track, using the array spread operator inside a loop effectively recreates arrays on every iteration. This leads to amortized O(N^2) memory allocations and unnecessary garbage collection overhead, bottlenecking the build-time static generation and potential runtime queries.
📊 Impact
🔬 Measurement
Run
npm run testto verify no regressions in the list sorting functionality. Performance gains can be benchmarked on heavily populated environments using large arrays. All test snapshots passed perfectly validating output conformity.PR created automatically by Jules for task 2856021321514430546 started by @anyulled
Summary by CodeRabbit