Add an ordinal suffix to a number

JavaScript version

// `n` is a position number
const addOrdinal = (n) => `${n}${['st', 'nd', 'rd'][((((n + 90) % 100) - 10) % 10) - 1] || 'th'}`;

// Or
const addOrdinal = (n) => `${n}${[, 'st', 'nd', 'rd'][/1?.$/.exec(n)] || 'th'}`;

// Or
const addOrdinal = (n) => `${n}${[, 'st', 'nd', 'rd'][(n % 100 >> 3) ^ 1 && n % 10] || 'th'}`;

// Or
const addOrdinal = (n) => `${n}${{ one: 'st', two: 'nd', few: 'rd', other: 'th' }[new Intl.PluralRules('en', { type: 'ordinal' }).select(n)]}`;

TypeScript version

const addOrdinal = (n: number): string => `${n}${['st', 'nd', 'rd'][((((n + 90) % 100) - 10) % 10) - 1] || 'th'}`;

// Or
const addOrdinal = (n: number): string => `${n}${[, 'st', 'nd', 'rd'][/1?.$/.exec(n)] || 'th'}`;

// Or
const addOrdinal = (n: number): string => `${n}${[, 'st', 'nd', 'rd'][(n % 100 >> 3) ^ 1 && n % 10] || 'th'}`;

// Or
const addOrdinal = (n: number): string => `${n}${{ one: 'st', two: 'nd', few: 'rd', other: 'th' }[new Intl.PluralRules('en', { type: 'ordinal' }).select(n)]}`;

Examples

addOrdinal(1); // '1st'
addOrdinal(2); // '2nd'
addOrdinal(3); // '3rd'
addOrdinal(11); // '11th'
addOrdinal(12); // '13th'
addOrdinal(13); // '13th'