# kana-romaji, kana to alphabet converting library

Hiragana is transformed into lower case output.
Katakana is transformed into UPPER case output.
```js
toRomaji('ローマじ') // === 'RŌMAji';
```
The sequences of same vowels and 'ou' output with prolonged vowel of the first.
The sequence of 'ei' is not represented with long 'e'.
ex)
- 'ちちゅうかい', 'chichūkai'
- 'ふりょう', 'furyō'
- 'しょうがくせい', 'shōgakusei'

## Caveat
The rule to not consider as prolonged vowel sound
when the consecutive vowels are from separate Kanjis is not respected.

ex) 'きいはんとうのばあい'
- OK: 'kiihantōnobaai'
- Our _wrong_ output: 'kīhantōnobāi'

## Usage
### Typescript or modern es
```js
import { toRomaji } from 'kana-romaji';

if (toRomaji('ローマじ') === 'RŌMAji') {
    // do your work
}
```

### Old common JS
```js
var kanaRomaji = require("kana-romaji")

console.log(kanaRomaji.toRomaji('おばあさん'))
```

## What about wanakana?
WanaKana https://github.com/WaniKani/WanaKana offers various conversions between Kana and Romaji. Their functionality was somewhat limited in terms of rules of Romaji. Sequences of vowels 'おう' in 'こうこうせい' are transformed into 'ou' as in '*koukousei*' instead of '**kōkōsei**'. Despite all above, I appraise them! Thank you for being the inspiration!

## References
University of Tokyo had the following document for recommended Romaji representation.
- https://park.itc.u-tokyo.ac.jp/eigo/UT-Komaba-Nihongo-no-romaji-hyoki-v1.pdf

## I use this!
I'm using this library inside `word-decks` https://github.com/mtomim/word-decks project, a simple learning-card application.

# Updates
### 0.1.10 (2024)
- Correction of issue #1, namely, "てぃ" => "tei" instead of "ti"
- Use apostrophe (’) instead of hyphen (-) after 'n' and before a vowel (or 'y') when they are not to be pronounced together

ex. ほんや => hon’ya, ほにゃ => honya
- Prefer using 'n' for ん even before 'p', 'b' or 'm'

### 0.1.11 (2026)
- **Fixed long vowel sequence handling**: Correctly processes combinations of syllables followed by vowel-only characters and long vowel markers (e.g., `ユキノオー` → `YUKINOŌ`)
- **Fixed 'n' apostrophe issue**: Prevents incorrect apostrophes before numbers and Latin characters (e.g., `ポリゴン２` → `PORIGON２` instead of `PORIGON'２`)