divine-mobile: Skill for Claude Code

JavaScript Regex: \b Word Boundary Fails with CJK Characters

Problem

JavaScript's \b (word boundary) assertion silently fails when used with CJK (Chinese/Japanese/Korean) characters. The regex compiles without error and runs without throwing, but it simply never matches CJK text that should match. This is particularly insidious because:

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

Context / Trigger Conditions

• Regex pattern like /\b\u904B\u8EE2\u514D\u8A31\u8A3C\b/ (Japanese: 運転免許証) returns false on text containing the exact characters
• Pattern like /\b\uC6B4\uC804\uBA74\uD5C8\uC99D\b/ (Korean: 운전면허증) fails similarly
• Text-detection functions (e.g., hasDriverLicenceCue(), inferIssuerFromTitleText()) return incorrect results for CJK input while working correctly for all Latin-script patterns
• Any regex using \b boundaries around non-ASCII Unicode characters (also affects Cyrillic, Arabic, Thai, etc.)

Root Cause

JavaScript's \b matches the boundary between a "word character" (\w = [a-zA-Z0-9_]) and a "non-word character" (\W). CJK characters are classified as \W (non-word characters).

When \b appears before a CJK character, it looks for a \w-to-\W or \W-to-\w transition. But if the preceding character is also \W (whitespace, punctuation, start of string, or another CJK character), the boundary condition is \W-to-\W, which \b does NOT match.

// 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

Solution

Quick Fix: Remove \b from CJK patterns

Simply remove \b assertions from any regex pattern that matches CJK characters:

// 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