string-width

String width calculation is a hot path in terminal rendering — it's called on every line of output in tools like Ink, cli-truncate, wrap-ansi, and log-update. With the growth of AI-powered terminal agents that stream large amounts of text, this is becoming even more performance-sensitive. I profiled string-width and found two low-hanging optimizations: runs unconditionally even when no ANSI codes are present, and runs on every call even for pure ASCII input where width = length. ASCII + ANSI benchmarks (Apple M2 Max, Node 25.2.1) Non-ASCII inputs (CJK, emoji, mixed) are unaffected — they fall through to the existing path. PRs https://github.com/sindresorhus/string-width/pull/72 — ASCII fast path + stripAnsi guard https://github.com/chalk/strip-ansi/pull/54 — adds fast path to strip-ansi https://github.com/sindresorhus/get-east-asian-width/pull/14 — packed arrays with binary search (3.5x faster, -25% bundle size) Optimizations 1. ASCII fast path — regex detects pure printable ASCII, returns directly. Skips , regex, and EAW lookup entirely. 61x faster for short ASCII, the most common input type. 2. stripAnsi guard — check before calling . Avoids the overhead of strip-ansi's regex on strings that contain no ANSI escapes. 14x faster for ANSI-free short strings.