Pluralize and format lists
Hand-rolled pluralization like adding an s breaks as soon as you leave English. Intl.PluralRules tells you which grammatical category a number falls into for a locale, and Intl.ListFormat joins items with the right separators and conjunction. This example shows both.
English has two plural categories, one and other.
const english = new Intl.PluralRules("en-US");
console.log(english.select(1)); // one
console.log(english.select(2)); // other
console.log(english.select(0)); // other
console.log(english.resolvedOptions().pluralCategories); // [ "one", "other" ]Polish has four. Numbers ending in 2 to 4 use few, most others use many, and fractions fall back to other.
const polish = new Intl.PluralRules("pl");
console.log(polish.select(1)); // one
console.log(polish.select(2)); // few
console.log(polish.select(5)); // many
console.log(polish.select(22)); // few
console.log(polish.select(1.5)); // otherArabic uses all six categories, including zero, one, and two.
const arabic = new Intl.PluralRules("ar");
console.log(arabic.select(0)); // zero
console.log(arabic.select(1)); // one
console.log(arabic.select(2)); // two
console.log(arabic.select(6)); // few
console.log(arabic.select(15)); // manyA pluralize helper maps each category to a word form. For English you only need two forms.
const fileForms: Record<string, string> = { one: "file", other: "files" };
function pluralize(count: number): string {
return `${count} ${fileForms[english.select(count)]}`;
}
console.log(pluralize(1)); // 1 file
console.log(pluralize(3)); // 3 files
console.log(pluralize(0)); // 0 filesIntl.ListFormat joins arrays the way prose does. The conjunction type produces an and list, including the Oxford comma for en-US.
const and = new Intl.ListFormat("en-US", { type: "conjunction" });
console.log(and.format(["red", "green", "blue"])); // red, green, and blue
console.log(and.format(["red", "green"])); // red and greenThe disjunction type produces an or list.
const or = new Intl.ListFormat("en-US", { type: "disjunction" });
console.log(or.format(["red", "green", "blue"])); // red, green, or blueOther locales swap in their own conjunctions and comma rules.
const german = new Intl.ListFormat("de-DE", { type: "conjunction" });
console.log(german.format(["rot", "grün", "blau"])); // rot, grün und blauRun this example locally using the Deno CLI:
deno run https://docs.deno.com/examples/scripts/intl_plural_list.ts