wcwidth-o1 – Find Unicode text cell width in no time for JavaScript/TS

In plain words

wcwidth-o1 is a TypeScript library that calculates how many character cells Unicode text occupies on screen. It uses bitset lookups to achieve constant-time performance and supports the full Unicode 15.1 standard for combining characters. The tool is designed for JavaScript and TypeScript developers who need accurate text width measurements for terminal applications, text formatting, or display calculations.

written from the facts on this page · September 2026

From the sources

glibc-based POSIX wcwidth/wcswidth for Node.js & TypeScript - dawsonhuang0/Wcwidth-O1

A TypeScript/JavaScript implementation of glibc’s wcwidth(3) and wcswidth(3) , optimized to O(1) . Conforms to POSIX.1-2008 (IEEE Std 1003.1) for terminal column width calculation. wcwidth(3) is a per-code-point API and this package faithfully follows it. HOWEVER , multi-code-point sequences (emoji ZWJ, variation selectors, flags) may measure wider than what modern terminals draw. If you need to handle them, check out char-width . When a new Unicode version is released, the lookup table must be regenerated to follow the latest character width definitions. ./genTable.sh If your environment is not glibc-based, you'll see: [ WARNING ] Please compile on a glibc-based Linux distro (e.g. Debian).…from github.com

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