6.1.0 • Public • Published

FormatJS Extract CLDR Data

Utility library that extracts the CLDR data that's needed by the FormatJS libraries.

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This package offers a function to extract the CLDR data needed by the FormatJS libraries via its default export. The data is returned as an object keyed by locale language tags; e.g., "en-US". This package leverages the fact that language tags are hierarchical and will only return the unique, de-duplicated data that's needed.

The following example shows how the locale hierarchy is used to return the unique data:

var extractData = require('formatjs-extract-cldr-data');

var data = extractData({
    locales    : ['en-US', 'en-GB'],
    pluralRules: true

console.log(data); // =>

{ 'en-US': { locale: 'en-US', parentLocale: 'en' },
  'en-GB': { locale: 'en-GB', parentLocale: 'en-001' },
  'en-001': { locale: 'en-001', parentLocale: 'en' } },
  en: { locale: 'en', pluralRuleFunction: [Function] }

Since the pluralRuleFunction for the root locale "en" is the same as used in the locales: "en-US" and "en-GB", the function is located in the "en" entry. The entries for the en-* locales all contain a parentLocale property which can be followed up to "en".

Data Shape

The data object returned from this package will have the following shape, here's the data for US English:

{ en:
   { locale: 'en',
     pluralRuleFunction: [Function],
      { year: [Object],
        "year-short": [Object],
        month: [Object],
        "month-short": [Object],
        day: [Object],
        "day-short": [Object],
        hour: [Object],
        "hour-short": [Object],
        minute: [Object],
        "minute-short": [Object],
        second: [Object],
        "second-short": [Object] } } }

Each field has the following shape, here's the data for English year:

{ displayName: 'Year',
  relative: { '0': 'this year', '1': 'next year', '-1': 'last year' },
   { future: { one: 'in {0} year', other: 'in {0} years' },
     past: { one: '{0} year ago', other: '{0} years ago' } } }


In order for any data to be returned, the value true must be assigned to either the pluralRules and/or relativeFields options. By default, data will be returned for all locales in the CLDR; to limit which locales, assign an array of them to the locales option.


An optional array of locales to extract data for, specified as string language tags. By default, data will be returned for all locales in the CLDR.

Note: This package leverages the language tag hierarchy to de-duplicate data and also normalizes the casing of language tags. There will be an entry for every locale specified in locales, plus an entry to each parent locale up to the root. When a locale has a parent, a parentLocale field will be present in that locale's entry.


Boolean for whether or not pluralRuleFunctions should be extracted for the specified locales. These functions will support both cardinal and ordinal pluralization. These functions are generated using the make-plural project.


Boolean for whether or not fields should be extracted for the specified locales. The field data that's extracted is limited to the data required to support FormatJS' relative time formatting features, and it's organized in the shape described above.

Updating the CLDR Data

The CLDR version and data used by this package can be easily updated by changing the cldr-* package versions in package.json.

Note: It's recommended to keep the package versions exact and not use ~ or ^ modifiers.


This software is free to use under the Yahoo Inc. BSD license. See the LICENSE file for license text and copyright information.

The CLDR data contained in this packaged is licensed under the Apache, ICU, and Unicode licenses. See the CLDR license files for their license text and copyright information.



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