formatDecimal split digits with /(\d+?)(?=(\d{3})+(?!\d)|$)/g, whose
lookahead rescans the rest of a digit run at every position: quadratic in
the run's length (CodeQL js/polynomial-redos, high; inherited unchanged
from upstream). 20k digits took 258 ms, 200k about 25 s.
A loop now finds the same groups: within each digit run a group ends where
the digits left are a positive multiple of three, or at the end of the
string. Identical output to the pattern on 210,000 random inputs plus the
edge cases (letters around digits, short runs, negatives); 200k digits take
7 ms. The new spec case for a 60k-digit number fails on the old code.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
The header rule takes the current year as the end of the range, as upstream's
does; 581 sources still ended at 2025, which failed lint. Lint never ran to
completion here, so this went unseen.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
