wcwidth.js

wcwidth.js: A JavaScript Porting of Markus Kuhn's wcwidth() Implementation

wcwidth.js is a simple JavaScript porting of wcwidth() implemented in C by Markus Kuhn.

wcwidth() and its string version, wcswidth() are defined by IEEE Std 1002.1-2001, a.k.a. POSIX.1-2001, and return the number of columns used to represent the given wide character and string. Markus's implementation assumes the wide character given to those functions to be encoded in ISO 10646, which is almost true for JavaScript's characters.

For convenience, wcwidth.js sets the getter of the property named wcwidth for the string type. You don't need to invoke a function to get the width of strings, but inspecting the wcwidth property is enough. The following code snippet shows how to use wcwidth.js:

var wcwidth = require('wcwidth')({
    nul:         0,
    control:     -1,
    monkeypatch: true
});    // equivalent to var wcwidth = require('wcwidth')();

console.log("한글".wcwidth);    // prints 4
console.log("\0".wcwidth);      // prints 0
console.log("\t".wcwidth);      // prints -1

The argument { nul: 0, control: -1, monkeypatch: true } (which are the default values, in fact) tells wcwidth.js to return 0 for the NUL character and -1 for non-printable control characters. Setting a negative value to nul or control makes the wcwidth property set to -1 for any string that contains NUL or control characters respectively. If you plan to replace each control character with, say, ??? when printing, you can 'require' wcwidth.js as follows:

var wcwidth = require('wcwidth')({
    control: 3
});    // leaving nul as 0

console.log("\t".wcwidth);    // prints 3
console.log("\0".wcwidth);    // prints 0

The last option monkeypatch allows wcwidth.js to monkey-patch String.prototype to provide the getter wcwidth. Even if it is convenient to have a getter that looks like the native one, it is sometimes unwanted as adding a getter into String.prototype may break node.js's module system; you are not guaranteed to have the version your code requires through the getter if other modules you're using also depend on other versions of wcwidth.js (thanks to timoxley for the information). By setting monkeypatch to false, wcwidth.js touches no global object and provides no getter but a callable method explained below.

wcwidth.js also provides a method. Since JavaScript has no character type, it is meaningless to have two versions while POSIX does for C. The method also accepts a code value that can be obtained by the charCodeAt() method.

console.log(wcwidth('한'));                 // prints 2
console.log(wcwidth('글'.charCodeAt(0));    // prints 2
console.log(wcwidth('한글'));               // prints 4

INSTALL.md explains how to build and install the library. For the copyright issues, see the accompanying LICENSE.md file.

If you have a question or suggestion, do not hesitate to contact me via email (woong.jun at gmail.com) or web (http://code.woong.org/).