TS Get unicode aware string length (1 char for every emoji char)

strings.spec.ts

import { getUnicodeAwareStringLength } from './strings';

describe('strings -> getUnicodeAwareStringLength', () => {
    it('should work for a regular string', () => {
        expect(getUnicodeAwareStringLength('foo')).toBe(3);
    });

    it('should work for an emoji string', () => {
        expect(getUnicodeAwareStringLength('🚗🚗')).toBe(2);
    });

    it('should return 1 for a simple emoji', () => {
        expect(getUnicodeAwareStringLength('👾')).toBe(1);
    });

    it('should return 2 for a emoji with skin tone modifier', () => {
        expect(getUnicodeAwareStringLength('🙋🏽')).toBe(1);
    });

    it('should return 3 for a emoji sequence using combining glyph', () => {
        expect(getUnicodeAwareStringLength('🧑‍💻')).toBe(1);
    });

    it('should return 7 for a four-emoji sequence using 3 combining glyphs', () => {
        expect(getUnicodeAwareStringLength('👨‍👩‍👧‍👦')).toBe(1);
    });
});

strings.ts

// https://www.mmbyte.com/article/41645.html (Answer 2)
export const getUnicodeAwareStringLength = (str: string): number => {
    const joiner = '\u{200D}';
    const split = str.split(joiner);
    let count = 0;

    const REGEXP_EMOJI_VARIATION = /[\ufe00-\ufe0f]/g;
    // http://www.unicode.org/reports/tr51/#Diversity
    const REGEXP_SKIN_TONE_MODIFIER = /[\u{1F3FB}-\u{1F3FF}]/gu;

    for (const s of split) {
        count += Array.from(s.replace(REGEXP_EMOJI_VARIATION, '').replace(REGEXP_SKIN_TONE_MODIFIER, '')).length;
    }

    return count / split.length;
};