util: create hex style cache and fast path by araujogui · Pull Request #62999 · nodejs/node

araujogui · 2026-04-28T00:33:08Z

Improve styleText performance by caching and fast-path

Benchmark

util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='boolean'                -0.71 %       ±1.04%  ±1.38%  ±1.80%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='invalid'                 0.80 %       ±0.86%  ±1.14%  ±1.49%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='number'                 -0.59 %       ±0.93%  ±1.24%  ±1.62%
util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='string'         ***   1135.88 %      ±31.19% ±42.04% ±55.81%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='boolean'                -0.09 %       ±1.43%  ±1.90%  ±2.47%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='invalid'                -0.02 %       ±0.98%  ±1.30%  ±1.69%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='number'                  0.83 %       ±1.79%  ±2.40%  ±3.15%
util/style-text.js n=1000 validateStream=0 format='invalid' messageType='string'           *     -1.19 %       ±0.97%  ±1.29%  ±1.68%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='boolean'                 -0.24 %       ±1.16%  ±1.55%  ±2.02%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='invalid'                  0.60 %       ±0.92%  ±1.23%  ±1.60%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='number'                   0.81 %       ±1.22%  ±1.63%  ±2.14%
util/style-text.js n=1000 validateStream=0 format='italic' messageType='string'                   1.47 %       ±3.09%  ±4.12%  ±5.36%
util/style-text.js n=1000 validateStream=0 format='red' messageType='boolean'              *      1.17 %       ±1.03%  ±1.37%  ±1.79%
util/style-text.js n=1000 validateStream=0 format='red' messageType='invalid'                     0.73 %       ±0.99%  ±1.32%  ±1.72%
util/style-text.js n=1000 validateStream=0 format='red' messageType='number'                     -0.34 %       ±0.94%  ±1.25%  ±1.63%
util/style-text.js n=1000 validateStream=0 format='red' messageType='string'                      4.92 %       ±6.11%  ±8.17% ±10.72%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='boolean'                -0.50 %       ±1.32%  ±1.76%  ±2.29%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='invalid'                 0.62 %       ±0.89%  ±1.19%  ±1.56%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='number'                 -0.14 %       ±0.79%  ±1.06%  ±1.37%
util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='string'                 -0.27 %       ±1.23%  ±1.64%  ±2.14%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='boolean'                -0.31 %       ±0.97%  ±1.29%  ±1.68%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='invalid'                 0.61 %       ±0.85%  ±1.13%  ±1.48%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='number'                 -0.05 %       ±0.78%  ±1.04%  ±1.35%
util/style-text.js n=1000 validateStream=1 format='invalid' messageType='string'                  0.69 %       ±1.55%  ±2.07%  ±2.70%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='boolean'                 -0.01 %       ±1.07%  ±1.42%  ±1.85%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='invalid'                 -0.27 %       ±1.09%  ±1.45%  ±1.90%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='number'                   0.04 %       ±1.04%  ±1.38%  ±1.80%
util/style-text.js n=1000 validateStream=1 format='italic' messageType='string'                  -0.41 %       ±0.91%  ±1.21%  ±1.58%
util/style-text.js n=1000 validateStream=1 format='red' messageType='boolean'                     0.56 %       ±1.18%  ±1.57%  ±2.05%
util/style-text.js n=1000 validateStream=1 format='red' messageType='invalid'                    -0.41 %       ±0.94%  ±1.26%  ±1.64%
util/style-text.js n=1000 validateStream=1 format='red' messageType='number'                     -0.88 %       ±0.96%  ±1.28%  ±1.67%
util/style-text.js n=1000 validateStream=1 format='red' messageType='string'                     -0.04 %       ±1.00%  ±1.33%  ±1.73%

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Pull request overview

This PR improves util.styleText() performance for hex colors by introducing a cached hex-style lookup and a fast path for the common case where validateStream: false.

Changes:

Add a module-level hexStyleCache and helper (getHexStyle) to memoize computed ANSI sequences for #RGB/#RRGGBB.
Reuse a shared close sequence constant for 24-bit foreground colors (\u001b[39m) and integrate hex handling into the validateStream: false fast path.
Refactor hex handling in the main formatting loop to use cached sequences instead of re-parsing on every call.

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ljharb · 2026-04-28T01:43:44Z

+const hexStyleCache = { __proto__: null };



isn't the maximum possible permutations here 16,781,312 - is the memory size of 17 million key/value pairs a massive concern?

Great point, altought a LRU doesn't seem a bad idea

codecov · 2026-04-28T01:59:50Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.05%. Comparing base (bbf51ad) to head (5b9ea9d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62999      +/-   ##
==========================================
+ Coverage   90.03%   90.05%   +0.01%     
==========================================
  Files         713      713              
  Lines      224950   224977      +27     
  Branches    42532    42540       +8     
==========================================
+ Hits       202542   202596      +54     
+ Misses      14175    14170       -5     
+ Partials     8233     8211      -22

Files with missing lines	Coverage Δ
lib/util.js	`94.49% <100.00%> (+0.23%)`	⬆️

... and 31 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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Renegade334 · 2026-04-29T02:16:57Z

+const kHexCloseSeq = kEscape + '39' + kEscapeEnd;
+
 let styleCache;
+const hexStyleCache = { __proto__: null };


I note the benchmarks are all repeating the same lookup – I imagine that using a plain object as the map here could end up deoptimising if the cache miss rate is high, eg. colours being randomised by the user? Appreciate this is probably quite niche in reality, but might be worth a benchmark case to see how something like a SafeMap would compare.

There aren’t major differences.

Benchmark

util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='boolean' -1.31 % ±3.83% ±5.10% ±6.64% util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='invalid' -4.67 % ±7.12% ±9.54% ±12.55% util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='number' -0.30 % ±2.97% ±3.95% ±5.15% util/style-text.js n=1000 validateStream=0 format='#ff0000' messageType='string' * 3.74 % ±3.70% ±4.94% ±6.44% util/style-text.js n=1000 validateStream=0 format='#rotating' messageType='boolean' -1.08 % ±3.55% ±4.72% ±6.15% util/style-text.js n=1000 validateStream=0 format='#rotating' messageType='invalid' -4.76 % ±7.76% ±10.39% ±13.66% util/style-text.js n=1000 validateStream=0 format='#rotating' messageType='number' -0.09 % ±3.19% ±4.25% ±5.54% util/style-text.js n=1000 validateStream=0 format='#rotating' messageType='string' 0.74 % ±4.17% ±5.55% ±7.22% util/style-text.js n=1000 validateStream=0 format='invalid' messageType='boolean' 0.72 % ±6.24% ±8.33% ±10.89% util/style-text.js n=1000 validateStream=0 format='invalid' messageType='invalid' -1.52 % ±3.46% ±4.60% ±6.00% util/style-text.js n=1000 validateStream=0 format='invalid' messageType='number' 0.46 % ±3.20% ±4.27% ±5.56% util/style-text.js n=1000 validateStream=0 format='invalid' messageType='string' 1.16 % ±3.10% ±4.13% ±5.38% util/style-text.js n=1000 validateStream=0 format='italic' messageType='boolean' -1.15 % ±4.42% ±5.93% ±7.79% util/style-text.js n=1000 validateStream=0 format='italic' messageType='invalid' -3.32 % ±3.57% ±4.75% ±6.18% util/style-text.js n=1000 validateStream=0 format='italic' messageType='number' 1.35 % ±3.67% ±4.88% ±6.35% util/style-text.js n=1000 validateStream=0 format='italic' messageType='string' -1.02 % ±4.64% ±6.18% ±8.04% util/style-text.js n=1000 validateStream=0 format='red' messageType='boolean' -2.72 % ±3.47% ±4.61% ±6.01% util/style-text.js n=1000 validateStream=0 format='red' messageType='invalid' -1.47 % ±3.57% ±4.76% ±6.20% util/style-text.js n=1000 validateStream=0 format='red' messageType='number' -1.55 % ±2.97% ±3.96% ±5.15% util/style-text.js n=1000 validateStream=0 format='red' messageType='string' -0.42 % ±4.55% ±6.05% ±7.88% util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='boolean' 0.65 % ±5.41% ±7.21% ±9.42% util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='invalid' * -3.55 % ±2.88% ±3.83% ±4.99% util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='number' -1.31 % ±3.15% ±4.20% ±5.48% util/style-text.js n=1000 validateStream=1 format='#ff0000' messageType='string' 3.73 % ±4.20% ±5.59% ±7.29% util/style-text.js n=1000 validateStream=1 format='#rotating' messageType='boolean' -1.73 % ±4.42% ±5.89% ±7.70% util/style-text.js n=1000 validateStream=1 format='#rotating' messageType='invalid' -2.71 % ±4.63% ±6.17% ±8.03% util/style-text.js n=1000 validateStream=1 format='#rotating' messageType='number' -0.79 % ±4.14% ±5.52% ±7.21% util/style-text.js n=1000 validateStream=1 format='#rotating' messageType='string' -0.28 % ±3.44% ±4.58% ±5.96% util/style-text.js n=1000 validateStream=1 format='invalid' messageType='boolean' 0.29 % ±5.79% ±7.70% ±10.02% util/style-text.js n=1000 validateStream=1 format='invalid' messageType='invalid' -3.20 % ±3.51% ±4.67% ±6.08% util/style-text.js n=1000 validateStream=1 format='invalid' messageType='number' -1.35 % ±2.60% ±3.46% ±4.50% util/style-text.js n=1000 validateStream=1 format='invalid' messageType='string' 1.61 % ±2.64% ±3.51% ±4.58% util/style-text.js n=1000 validateStream=1 format='italic' messageType='boolean' 0.52 % ±4.47% ±5.95% ±7.76% util/style-text.js n=1000 validateStream=1 format='italic' messageType='invalid' 2.16 % ±6.08% ±8.14% ±10.70% util/style-text.js n=1000 validateStream=1 format='italic' messageType='number' -0.13 % ±3.02% ±4.01% ±5.22% util/style-text.js n=1000 validateStream=1 format='italic' messageType='string' 0.73 % ±3.93% ±5.24% ±6.83% util/style-text.js n=1000 validateStream=1 format='red' messageType='boolean' -0.30 % ±3.44% ±4.59% ±5.98% util/style-text.js n=1000 validateStream=1 format='red' messageType='invalid' -0.79 % ±4.18% ±5.57% ±7.25% util/style-text.js n=1000 validateStream=1 format='red' messageType='number' -1.35 % ±3.39% ±4.51% ±5.87% util/style-text.js n=1000 validateStream=1 format='red' messageType='string' 1.11 % ±3.21% ±4.27% ±5.57% Be aware that when doing many comparisons the risk of a false-positive result increases. In this case, there are 40 comparisons, you can thus expect the following amount of false-positive results: 2.00 false positives, when considering a 5% risk acceptance (*, **, ***), 0.40 false positives, when considering a 1% risk acceptance (**, ***),

Signed-off-by: Guilherme Araújo <arauujogui@gmail.com>

araujogui · 2026-05-09T03:20:56Z

CC @nodejs/performance

Copilot AI review requested due to automatic review settings April 28, 2026 00:33

nodejs-github-bot added needs-ci PRs that need a full CI run. util Issues and PRs related to the built-in util module. labels Apr 28, 2026

Copilot started reviewing on behalf of araujogui April 28, 2026 00:33 View session

Copilot AI reviewed Apr 28, 2026

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araujogui force-pushed the improve-styletext branch from c879174 to 521eba3 Compare May 8, 2026 22:46

araujogui added 3 commits May 8, 2026 21:08

util: create hex style cache and fast path

512ce5b

Signed-off-by: Guilherme Araújo <arauujogui@gmail.com>

util: skip getHexStyle() when colorization is disabled

bcf6f74

benchmark: create rotating hex benchmark

5b9ea9d

araujogui force-pushed the improve-styletext branch from 521eba3 to 5b9ea9d Compare May 9, 2026 00:08

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util: create hex style cache and fast path#62999

util: create hex style cache and fast path#62999
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