@pointnet/cldr-spellout

Documentation & live playground →

TypeScript implementation of ICU Rule-Based Number Formatting (RBNF) — converts numbers to words across 89 CLDR locales.

import { RuleBasedNumberFormat } from "@pointnet/cldr-spellout";

const fmt = RuleBasedNumberFormat.fromLocale("en");
fmt.format(123);                      // "one hundred twenty-three"
fmt.format(1, "%digits-ordinal");     // "1st"
fmt.parse("forty-two");               // 42

Features

• 89 CLDR locales — all locales from cldr-rbnf v48 (Unicode CLDR 48)
• Spellout & ordinals — cardinal numbers, ordinals, and more depending on locale
• Parse — convert spelled-out text back to numbers
• Custom rules — construct a formatter from your own RBNF rule string
• Synchronous — no async, no dynamic imports; works in Node.js and browsers
• Dual ESM/CJS — ships both formats; tree-shakeable ("sideEffects": false)

Installation

npm install @pointnet/cldr-spellout

Requires Node.js ≥ 24 (for native ESM JSON imports). Browser bundles are unaffected.

Usage

Load a built-in locale

import { RuleBasedNumberFormat } from "@pointnet/cldr-spellout";

const en = RuleBasedNumberFormat.fromLocale("en");
en.format(1000);   // "one thousand"
en.format(0.5);    // "zero point five"
en.format(-7);     // "minus seven"

const fr = RuleBasedNumberFormat.fromLocale("fr");
fr.format(71);     // "soixante-et-onze"
fr.format(80);     // "quatre-vingts"

const de = RuleBasedNumberFormat.fromLocale("de");
de.format(42);     // "zweiundvierzig"

Ordinals and other rule sets

Each locale exposes one or more named rule sets. Pass a rule set name as the second argument to format():

const en = RuleBasedNumberFormat.fromLocale("en");

en.format(1,  "%digits-ordinal");  // "1st"
en.format(2,  "%digits-ordinal");  // "2nd"
en.format(13, "%digits-ordinal");  // "13th"

// List available rule sets
en.getRuleSetNames();
// → ["%spellout-numbering", "%spellout-numbering-year",
//    "%spellout-cardinal", "%spellout-ordinal", "%digits-ordinal", ...]

Parse words to a number

const en = RuleBasedNumberFormat.fromLocale("en");
en.parse("one hundred twenty-three");  // 123
en.parse("forty-two");                 // 42

Load from raw CLDR data

fromCldrData() accepts any object matching the IRBNFData shape — useful when you supply your own rule data rather than a locale file:

import { RuleBasedNumberFormat } from "@pointnet/cldr-spellout";
import type { IRBNFData } from "@pointnet/cldr-spellout";

const durationData: IRBNFData = {
  rbnf: {
    identity: { language: "en" },
    rbnf: {
      DurationRules: {
        "%%min-sec":  [["0", ":=00="]],
        "%duration":  [
          ["0",        "=%%seconds="],
          ["60/60",    "<0<>%%min-sec>"],
          ["3600/3600","<0<:>%%min-sec>"],
        ],
        "%%seconds":  [
          ["0", "0 sec."],
          ["1", "1 sec."],
          ["2", "=#,##0= sec."],
        ],
      },
    },
  },
};

const fmt = RuleBasedNumberFormat.fromCldrData(durationData);
fmt.format(3662);  // "1:01:02"

Custom rule string

You can construct a formatter from any ICU RBNF rule description string:

import { RuleBasedNumberFormat } from "@pointnet/cldr-spellout";

// Custom duration rules (adapted from ICU test suite)
const rules = `
%%min-sec:
    0: :=00=;
%duration:
    0: =%%seconds=;
    60/60: <0<>%%min-sec>;
    3600/3600: <0<:>%%min-sec>;
%%seconds:
    0: 0 sec.;
    1: 1 sec.;
    2: =#,##0= sec.;
`;

const fmt = new RuleBasedNumberFormat(rules, "en");
fmt.format(3662);  // "1:01:02"

API

Static methods

Method	Description
RuleBasedNumberFormat.fromLocale(locale)	Create a formatter from a built-in CLDR locale. Throws if the locale is unsupported.
RuleBasedNumberFormat.fromCldrData(data, locale?)	Create a formatter from a raw IRBNFData object. locale defaults to the identity in the JSON.
RuleBasedNumberFormat.getSupportedLocales()	Returns an array of all 89 supported BCP 47 locale tags.

Constructor

new RuleBasedNumberFormat(rules: string, locale?: string)

Construct from an ICU RBNF rule description string. locale is a BCP 47 tag used for Intl.NumberFormat / Intl.PluralRules (default: "en").

Instance methods

Method	Description
format(number, ruleSetName?)	Format a number to text. Uses the default rule set unless ruleSetName is given.
parse(text)	Parse spelled-out text back to a number. Tries all public rule sets and returns the best match.
getRuleSetNames()	Returns all public rule set names (e.g., ["%spellout-numbering", "%digits-ordinal"]).
getDefaultRuleSetName()	Returns the name of the active default rule set.
setDefaultRuleSet(name)	Change the default rule set used when format() is called without a rule set name.
getRules()	Returns the original rule description string.

Types

import type { IRBNFData } from "@pointnet/cldr-spellout";

IRBNFData is the shape of a cldr-rbnf locale JSON file, accepted by fromCldrData().

Supported Locales

89 BCP 47 locale tags:

af ak am ar az be bg bs ca ccp chr cs cy da de de-CH ee el en en-IN eo es es-419 et fa fa-AF ff fi fil fo fr fr-BE fr-CH ga gu he hi hr hu hy id is it ja ka kk kl km ko ky lb lo lrc lt lv mk ms mt my ne nl nn no pl pt pt-PT qu ro ru se sk sl sq sr sr-Latn su sv sw ta th tr uk und vec vi yue yue-Hans zh zh-Hant

Use RuleBasedNumberFormat.getSupportedLocales() at runtime to get the full list.

License

MIT © pointnet