locutus/esm/php/var/is_unicode.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

export function is_unicode(vr) {
    //  discuss at: https://locutus.io/php/is_unicode/
    // original by: Brett Zamir (https://brett-zamir.me)
    //      note 1: Almost all strings in JavaScript should be Unicode
    //   example 1: is_unicode('We the peoples of the United Nations...!')
    //   returns 1: true
    if (typeof vr !== 'string') {
        return false;
    }
    // If surrogates occur outside of high-low pairs, then this is not Unicode
    let arr;
    const highSurrogate = '[\uD800-\uDBFF]';
    const lowSurrogate = '[\uDC00-\uDFFF]';
    const highSurrogateBeforeAny = new RegExp(highSurrogate + '([\\s\\S])', 'g');
    const lowSurrogateAfterAny = new RegExp('([\\s\\S])' + lowSurrogate, 'g');
    const singleLowSurrogate = new RegExp('^' + lowSurrogate + '$');
    const singleHighSurrogate = new RegExp('^' + highSurrogate + '$');
    while ((arr = highSurrogateBeforeAny.exec(vr)) !== null) {
        if (!arr[1] || !singleLowSurrogate.test(arr[1])) {
            // If high not followed by low surrogate
            return false;
        }
    }
    while ((arr = lowSurrogateAfterAny.exec(vr)) !== null) {
        if (!arr[1] || !singleHighSurrogate.test(arr[1])) {
            // If low not preceded by high surrogate
            return false;
        }
    }
    return true;
}