¿Cómo pluralizar un string basado en el lenguaje en Javascript?

function pluralize(locale, count, singular, plural) {
    const pluralRules = new Intl.PluralRules(locale);
    const numbering = pluralRules.select(count);
    switch (numbering) {
        case 'one':
        return count + ' ' + singular;
        case 'other':
        return count + ' ' + plural;
        default:
        throw new Error('Unknown: '+ numberig);
    }
}

function showItemsQuantity(count) {
    return pluralize('en-US', count, 'item', 'items')
}

const zeroItem = showItemsQuantity(0) // 0 items
const oneItem = showItemsQuantity(1) // 1 item
const manyItem = showItemsQuantity(12) // 12 items

// Spanish
function mostrarCantidadCajas(count) {
    return pluralize('es-ES', count, 'caja', 'cajas')
}
const ceroItem = mostrarCantidadCajas(0) // 0 cajas
const unoItem = mostrarCantidadCajas(1) // 1 caja
const muchosItem = mostrarCantidadCajas(12) // 12 cajas

const suffixes = new Map([
  ['zero',  'cathod'],
  ['one',   'gath'],
  // Note: the `two` form happens to be the same as the `'one'`
  // form for this word specifically, but that is not true for
  // all words in Welsh.
  ['two',   'gath'],
  ['few',   'cath'],
  ['many',  'chath'],
  ['other', 'cath'],
]);
const pr = new Intl.PluralRules('cy');
const formatWelshCats = (n) => {
  const rule = pr.select(n);
  const suffix = suffixes.get(rule);
  return `${n} ${suffix}`;
};

formatWelshCats(0);   // '0 cathod'
formatWelshCats(1);   // '1 gath'
formatWelshCats(1.5); // '1.5 cath'
formatWelshCats(2);   // '2 gath'
formatWelshCats(3);   // '3 cath'
formatWelshCats(6);   // '6 chath'
formatWelshCats(42);  // '42 cath'

const pr = new Intl.PluralRules('en-US',{
    type: 'ordinal'
})
const suffixes = {
    one: 'st',
    two: 'nd',
    few: 'rd',
    other: 'th'
}

const formatOrdinals = n => `${n}${suffixes[pr.select(n)]}`
formatOrdinals(0) // 0th
formatOrdinals(1) //1sst
formatOrdinals(2) // //2nd
formatOrdinals(40) //40th
formatOrdinals(63) // 63rd
formatOrdinals(100) // 100nd