perf(context): iterate the header record with for..in

[yusukebe]

This PR is one of the performance improvements.

Object.entries(headers) creates a throwaway array of [key, value] every time, but for (const k in headers) does not. So replacing them will introduce improvement. This affects query GET /id/1?name=bun and body POST /json.

Bun

$ ROUNDS=5 ./compare.sh
round 1/5: main -> dev
round 2/5: dev -> main
round 3/5: main -> dev
round 4/5: dev -> main
round 5/5: main -> dev
• ping GET /
  main             median  300.11 ns  rounds: [295.27 ns, 302.92 ns, 300.11 ns, 311.90 ns, 288.84 ns]
  dev              median  298.71 ns  rounds: [299.84 ns, 315.35 ns, 294.86 ns, 292.81 ns, 298.71 ns]
  summary: dev is 1.00x faster than main (median of round avgs)

• query GET /id/1?name=bun
  main             median  746.01 ns  rounds: [740.26 ns, 739.86 ns, 746.01 ns, 762.05 ns, 764.40 ns]
  dev              median  695.33 ns  rounds: [677.73 ns, 695.33 ns, 705.45 ns, 704.78 ns, 695.18 ns]
  summary: dev is 1.07x faster than main (median of round avgs)

• body POST /json
  main             median    1.30 µs  rounds: [1.25 µs, 1.28 µs, 1.30 µs, 1.32 µs, 1.32 µs]
  dev              median    1.25 µs  rounds: [1.21 µs, 1.24 µs, 1.25 µs, 1.27 µs, 1.26 µs]
  summary: dev is 1.04x faster than main (median of round avgs)

Node.js

$ ROUNDS=5 RUNTIME=node ./compare.sh
round 1/5: main -> dev
round 2/5: dev -> main
round 3/5: main -> dev
round 4/5: dev -> main
round 5/5: main -> dev
• ping GET /
  main             median  898.68 ns  rounds: [902.06 ns, 897.78 ns, 897.73 ns, 898.68 ns, 910.96 ns]
  dev              median  890.24 ns  rounds: [889.80 ns, 879.75 ns, 890.24 ns, 896.93 ns, 906.54 ns]
  summary: dev is 1.01x faster than main (median of round avgs)

• query GET /id/1?name=bun
  main             median    1.57 µs  rounds: [1.57 µs, 1.58 µs, 1.57 µs, 1.57 µs, 1.51 µs]
  dev              median    1.52 µs  rounds: [1.50 µs, 1.45 µs, 1.55 µs, 1.52 µs, 1.52 µs]
  summary: dev is 1.03x faster than main (median of round avgs)

• body POST /json
  main             median    5.69 µs  rounds: [5.78 µs, 5.68 µs, 5.69 µs, 5.62 µs, 5.69 µs]
  dev              median    5.56 µs  rounds: [5.49 µs, 5.51 µs, 5.60 µs, 5.56 µs, 5.59 µs]
  summary: dev is 1.02x faster than main (median of round avgs)

---

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[github-actions]

HTTP Performance Benchmark

Framework	Runtime	Average	Ping	Query	Body
hono (origin/main)	bun	35,193.41	50,097.12	30,668.32	24,814.80
hono (current)	bun	36,150.29	49,943.86	32,461.04	26,045.97
Change		+2.72%	-0.31%	+5.85%	+4.96%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.08%. Comparing base (c285f9a) to head (ead16b5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5118   +/-   ##
=======================================
  Coverage   79.08%   79.08%           
=======================================
  Files         154      154           
  Lines       10764    10765    +1     
  Branches     2254     2254           
=======================================
+ Hits         8513     8514    +1     
  Misses       2251     2251           

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