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Steven Levithan @slevithan
Joined May 2008
  • Tweets 1,226
  • Following 195
  • Followers 812
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Stephan Schreiber created an open source VS Code extension that adds syntax highlighting for Regex tagged template strings! marketplace.visualstudio.com…

Regex - Visual Studio Marketplace

Extension for Visual Studio Code - Syntax highlighting for Regex tagged templates.

marketplace.visualstudio.com
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Regex 6.1.0 released. Adds even cleaner and more robust interpolation of RegExp instances and partial patterns. And improved docs. 😁
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github.com/slevithan/regex

GitHub - slevithan/regex: JS regexes ➕ future. A template tag for readable, high-performance,...

JS regexes ➕ future. A template tag for readable, high-performance, native JS regexes with extended syntax, context-aware interpolation, and always-on best practices. - slevithan/regex

github.com
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Oniguruma-To-ES now has 12M dl/m. Most of that comes from Shiki, which uses it to make VSCode-style syntax highlighting possible in native JS (no large WASM). I like to think it's contributing to Shiki's rapid growth :) Recent example is in Vercel's streamdown.ai
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Shiki's JS RegExp engine (for high quality syntax highlighting without WASM, built on top of my Oniguruma-To-ES library) now supports 100% of Shiki's 222 built-in languages 🎉 github.com/shikijs/shiki/pul…

docs: update js engine compat report by slevithan · Pull Request #1049 · shikijs/shiki

Reruns the JS engine compatibility report for Shiki 3.9.1. Swift is now supported, resulting in 100% language compatibility. 🎉 Minor docs updates.

github.com
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The latest version of Regex Colorizer (a project I started in 2007) is finally available via npm, after getting the package name transferred to me 😊 github.com/slevithan/regex-c…

GitHub - slevithan/regex-colorizer: 🎨 Highlighter for JavaScript regex syntax

🎨 Highlighter for JavaScript regex syntax. Contribute to slevithan/regex-colorizer development by creating an account on GitHub.

github.com
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Huge thanks to Divyansh Singh from the Vue core team for sponsoring my work on GitHub. 😊 github.com/sponsors/slevitha…
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Improved the docs for regex-recursion, highlighting standalone usage (without Regex ). Less than 2 kB for recursive regex matching with support for all ES2025 regex syntax. github.com/slevithan/regex-r…

GitHub - slevithan/regex-recursion: 🪆 Adds recursive matching to native JavaScript regexes

🪆 Adds recursive matching to native JavaScript regexes - slevithan/regex-recursion

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🚢 Released emoji-regex-xs v2.0. Now matches all underqualified emoji included in Unicode's emoji-test.txt list, to better match @mathias's excellent emoji-regex and real-world emoji use. Lib size reduced from 0.3 to 0.2 kB in the process :)
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Regular expressions should not change the length of a match based on case insensitivity. My case for a breaking change in Oniguruma: github.com/kkos/oniguruma/is…

Don't expand character match length with flag `i` (unless using a new flag) · Issue #351 · kkos/o...

Currently, Oniguruma sometimes applies Unicode's SpecialCasing.txt rules when using flag i, which can lengthen the match of a character, character class, or set (like \w or \S). For example, (?...

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The Onig optimizer (new release today!) built on the same parser github.com/slevithan/oniguru… is also in a class of its own, and has rapidly improved. (regexp-tree's optimizer is pretty good for JS regexes and was early inspiration, but the Onig version has surpassed it in many ways.)

GitHub - slevithan/oniguruma-parser: 🌿 Parse, validate, traverse, transform, and optimize Onigur...

🌿 Parse, validate, traverse, transform, and optimize Oniguruma regular expressions - slevithan/oniguruma-parser

github.com
Steven Levithan@slevithan
13 Apr 2025
oniguruma-to-es v4.2.0 shipped! 🚢 Continues improving by far the most sophisticated regex translator in the world. JS coders who've never used Oniguruma might still find it useful if they want much more feature-rich regexes (with native perf!) github.com/slevithan/oniguru…
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Steven Levithan retweeted
kishikawa katsumi 🍪@k_katsumi
6 Apr 2025
swiftregex.comをアップデートしてSwift Regexのデバッガを追加しました。パフォーマンスに影響するBacktrack数を調べたりステップごとに実行したりできます。
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oniguruma-to-es v4.2.0 shipped! 🚢 Continues improving by far the most sophisticated regex translator in the world. JS coders who've never used Oniguruma might still find it useful if they want much more feature-rich regexes (with native perf!) github.com/slevithan/oniguru…

GitHub - slevithan/oniguruma-to-es: 👹 Convert patterns from Oniguruma (the regex flavor used by...

👹 Convert patterns from Oniguruma (the regex flavor used by Ruby, TextMate grammars, etc.) to native JavaScript RegExp - slevithan/oniguruma-to-es

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oniguruma-parser v0.10.0 brings a bunch of quality of life improvements. 🚀 The regex optimizer it includes, which is probably the most interesting part for people who don't regularly use Oniguruma, has continued to improve! github.com/slevithan/oniguru…
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Migrated a bunch of tests from Jasmine to Vitest so I could use TypeScript more easily. Super nice! ⚡ Will be trying to use Vitest everywhere from now on.
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Over the last week, @TheRedCMD and I converted all of oniguruma-parser from JS to TS. 🎉 Surprised that all of this work uncovered 0 bugs (despite the high complexity of the migrated code), which I think speaks to the pre-existing quality of the lib. github.com/slevithan/oniguru…

GitHub - slevithan/oniguruma-parser: 🌿 Parse, validate, traverse, transform, and optimize Onigur...

🌿 Parse, validate, traverse, transform, and optimize Oniguruma regular expressions - slevithan/oniguruma-parser

github.com
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Request to run VS Code's syntax highlighting grammars through my Oniguruma regex optimizer (like Shiki does), which would improve highlighting performance for some languages like C and reduce the size of VS Code: github.com/microsoft/vscode/…

Pre-optimize all TM grammars for performance · Issue #243405 · microsoft/vscode

TextMate grammars used for syntax highlighting can individually contain thousands of regexes and are, collectively, quite large. Their regexes can be optimized via minification that also improves t...

github.com
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@fabiospampinato @kurtextrem I've updated the issue with some perf numbers: github.com/microsoft/vscode/… Roughly 30% perf improvement for C syntax highlighting just by running the regexes through the optimizer. No ReDoS fixes in C grammar; gains could be much higher if there were. (The VS Code issue doesn't mention Shiki's JS regex engine at all, but % perf gains from the optimizer in are similar across both Onig and JS engines.)
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