japanese-text-utils

Convert between full-width (Zenkaku) and half-width (Hankaku) characters in Japanese text.
Supports Katakana, ASCII letters/digits, spaces, punctuation, and symbols.

✨ Features

• Convert full-width → half-width (ガラス → ｶﾞﾗｽ)
• Convert half-width → full-width (ｶﾀｶﾅ → カタカナ)
• Handles:
  • Katakana (with dakuten/handakuten, e.g. ガ ↔ ｶﾞ, パ ↔ ﾊﾟ, ヴ ↔ ｳﾞ)
  • ASCII letters and digits (Ａ → A, ７ → 7, etc.)
  • Punctuation (! ↔ ！, $ ↔ ＄, etc.)
  • Spaces (　 ↔ " ")
  • Yen sign / backslash (￥ ↔ \)

📦 Installation

npm install japanese-text-utils
# or
yarn add japanese-text-utils
# or
pnpm add japanese-text-utils

🚀 Usage

ES Module / TypeScript

import { toHalfSizeCharacters, toFullSizeCharacters } from 'japanese-text-utils';

console.log(toHalfSizeCharacters('ガラス-１７個「テスト」'));
// => 'ｶﾞﾗｽ-17個｢ﾃｽﾄ｣'

console.log(toFullSizeCharacters('ｶﾀｶﾅ 123 ABC ~ \\\"'));
// => 'カタカナ　１２３　ＡＢＣ　～　￥"'

CommonJS

const { toHalfSizeCharacters, toFullSizeCharacters } = require('japanese-text-utils');

console.log(toHalfSizeCharacters('"'～　')); // => '"\'~ '
console.log(toFullSizeCharacters('"\'~ '));   // => '"'～　'

📚 API

toHalfSizeCharacters(str: string): string

Convert a string from full-width to half-width characters.

• Katakana: ガ → ｶﾞ, ア → ｱ
• ASCII letters/digits: Ａ → A, ７ → 7
• Punctuation: ！ → !, ＄ → $
• Spaces: 　 → " "
• ￥ → \

toFullSizeCharacters(str: string): string

Convert a string from half-width to full-width characters.

• Katakana: ｶﾞ → ガ, ｱ → ア
• ASCII letters/digits: A → Ａ, 7 → ７
• Punctuation: ! → ！, $ → ＄
• Spaces: " " → 　
• \ → ￥

🧪 Testing

You can run tests with Vitest or Jest. Example with Vitest:

npm install -D vitest

import { describe, it, expect } from 'vitest';
import { toHalfSizeCharacters, toFullSizeCharacters } from 'japanese-text-utils';

describe('Kana conversion', () => {
  it('converts full-width to half-width', () => {
    expect(toHalfSizeCharacters('ガ')).toBe('ｶﾞ');
  });
  it('converts half-width to full-width', () => {
    expect(toFullSizeCharacters('ｳﾞ')).toBe('ヴ');
  });
});