JS Regex Cjk Word Boundary

What it does

When your agent uses it

• Regex pattern with \b silently fails to match Japanese
• Pattern works for Latin/ASCII text but not CJK
• HasDriverLicenceCue
• Similar text-detection function returns false for CJK input despite correct characters

Example prompts

• “word characters”
• “/js-regex-cjk-word-boundary”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1No error is thrown — the regex just returns false
2. 2The same pattern works perfectly for Latin/ASCII text
3. 3The CJK characters in the pattern are correct (verified by direct string comparison)

What it can do on your machine

Read from SKILL.md and the folder at commit c3d6f7e. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are javascript).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • developer.mozilla.org
  • github.com
  • breakthebit.org
  • npmjs.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

JS Regex Cjk Word Boundary loads about 1.5k tokens when it runs. Until then it costs about 172 tokens; SKILL.md has 396 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~172

When it runs · the whole SKILL.md, loaded when a task matches

~1.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from divinevideo/divine-mobile at commit c3d6f7e, republished under its MPL-2.0 licence (© divinevideo). 396 words, ~1,499 tokens.

name

js-regex-cjk-word-boundary

description

Fix JavaScript regex failures when matching CJK (Chinese/Japanese/Korean) text using \b word boundaries. Use when: (1) Regex pattern with \b silently fails to match Japanese, Chinese, or Korean text, (2) Pattern works for Latin/ASCII text but not CJK, (3) hasDriverLicenceCue or similar text-detection function returns false for CJK input despite correct characters, (4) inferIssuerFromTitleText or pattern-matching functions fail on non-Latin scripts. Root cause: JavaScript \b only recognizes [a-zA-Z0-9_] as "word characters" — CJK characters are classified as \W (non-word), so \b before/after CJK always sees a non-word/non-word boundary and fails to match.

author

Claude Code

version

1.0.0

date

2026-03-09

// This FAILS — \b doesn't work with CJK
/\b\u904B\u8EE2\u514D\u8A31\u8A3C\b/.test("運転免許証")  // false!

// This WORKS — no word boundaries
/\u904B\u8EE2\u514D\u8A31\u8A3C/.test("運転免許証")  // true

// Before (broken):
[/\b\u904B\u8EE2\u514D\u8A31\u8A3C\b/, "JAPAN"],      // 運転免許証
[/\b\uC6B4\uC804\uBA74\uD5C8\uC99D\b/, "KOREA"],      // 운전면허증

// After (working):
[/\u904B\u8EE2\u514D\u8A31\u8A3C/, "JAPAN"],            // 運転免許証
[/\uC6B4\uC804\uBA74\uD5C8\uC99D/, "KOREA"],           // 운전면허증

// Unicode-aware approach (requires /v flag support):
/(?<=^|[\s\p{P}])\u904B\u8EE2\u514D\u8A31\u8A3C(?=$|[\s\p{P}])/v

// Manual boundary that works with CJK:
/(?<!\p{L})\u904B\u8EE2\u514D\u8A31\u8A3C(?!\p{L})/u

const patterns = [
  [/\bDRIVER'?S?\s+LICEN[CS]E\b/, "match"],   // Latin — \b works
  [/\bFÜHRERSCHEIN\b/, "match"],               // Latin+diacritics — \b works (Ü is \W but context helps)
  [/\u904B\u8EE2\u514D\u8A31\u8A3C/, "match"], // CJK — no \b needed
  [/\uC6B4\uC804\uBA74\uD5C8\uC99D/, "match"], // CJK — no \b needed
];

// Test that CJK matching works:
console.log(/\u904B\u8EE2\u514D\u8A31\u8A3C/.test("運転免許証"));  // true
console.log(/\uC6B4\uC804\uBA74\uD5C8\uC99D/.test("운전면허증"));  // true

// Verify it doesn't false-match substrings you don't want:
console.log(/\u904B\u8EE2\u514D\u8A31\u8A3C/.test("別の運転免許証テスト"));  // true (substring match is usually fine for CJK)

function hasDriverLicenceCue(text) {
  const combined = text.toUpperCase();
  return (
    /\bDRIVER'?S?\s+LICEN[CS]E\b/.test(combined) ||   // English
    /\bFÜHRERSCHEIN\b/.test(combined) ||               // German
    /\bPERMIS DE CONDUIRE\b/.test(combined) ||          // French
    /\u904B\u8EE2\u514D\u8A31\u8A3C/.test(combined) || // Japanese (no \b!)
    /\uC6B4\uC804\uBA74\uD5C8\uC99D/.test(combined)    // Korean (no \b!)
  );
}

© divinevideo, MPL-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .agents/skills/js-regex-cjk-word-boundary of divinevideo/divine-mobile.

Open the folder on GitHubat commit c3d6f7e