Japanese language detection

example.ts

const segmenter = new Intl.Segmenter(/*'ja', {granularity: 'grapheme'}*/);
const sufficientJapaneseCharactorRatio = 0.5; // XXX about 0.3 is preferable

function isJapaneseIntl(text: string) {
    let chars = 0;
    let japanese = 0;
    for (const seg of segmenter.segment(text)) {
        const char = seg.segment;
        // console.log(char);
        if (/[\u3040-\u309f\u30a0-\u30ff\u4e00-\u9faf\uff61-\uff9f]/.test(char)) japanese++;
        chars++;
    }
    return japanese / chars >= sufficientJapaneseCharactorRatio;
}

const texts: Array<string> = [
    "天才かっΣ(ﾟДﾟ)",
    "家族👨‍👩‍👧‍👦",
    "(´～｀)ﾓｸﾞﾓｸﾞ",
];

for (const text of texts) {
    console.log("testing: " + text);
    console.log("  isJapaneseIntl() : " + isJapaneseIntl(text));
}