Plural Rules by Language with Intl.PluralRules

Intl.PluralRules: Language-Specific Plural Categories

Different languages have different rules for plural forms. English has two (singular and plural), but other languages can have up to six. Intl.PluralRules determines which plural category a number belongs to.

Plural Categories

The possible categories are: zero, one, two, few, many, other.

English (2 categories)

const en = new Intl.PluralRules('en');
en.select(0);   // "other"
en.select(1);   // "one"
en.select(2);   // "other"
en.select(100); // "other"

Arabic (6 categories!)

const ar = new Intl.PluralRules('ar');
ar.select(0);   // "zero"
ar.select(1);   // "one"
ar.select(2);   // "two"
ar.select(3);   // "few"    (3-10)
ar.select(11);  // "many"   (11-99)
ar.select(100); // "other"  (100, 1000, ...)

Polish (4 categories)

const pl = new Intl.PluralRules('pl');
pl.select(1);   // "one"
pl.select(2);   // "few"    (2-4, 22-24, ...)
pl.select(5);   // "many"   (5-21, 25-31, ...)
pl.select(1.5); // "other"

Ordinal Plurals

const en = new Intl.PluralRules('en', { type: 'ordinal' });
en.select(1);   // "one"    -> "1st"
en.select(2);   // "two"    -> "2nd"
en.select(3);   // "few"    -> "3rd"
en.select(4);   // "other"  -> "4th"
en.select(21);  // "one"    -> "21st"

Practical Usage: Building Plural Messages

function pluralize(count, locale, forms) {
  const rule = new Intl.PluralRules(locale).select(count);
  return forms[rule] || forms.other;
}

pluralize(1, 'en', {
  one: '1 item',
  other: `${count} items`,
});
// "1 item"

pluralize(5, 'en', {
  one: '1 item',
  other: `${count} items`,
});
// "5 items"

Languages by Complexity

Categories	Languages
1 (other only)	Chinese, Japanese, Korean, Vietnamese, Thai
2 (one, other)	English, German, Spanish, Portuguese, Italian
3	French, Latvian, Romanian
4	Polish, Czech, Slovak, Slovenian
6	Arabic