Reverse CLDR

CLDR data is published as locale-oriented JSON files across several npm packages. That works well when reading one locale at a time, but it is inefficient when you need one functional area across many locales.

Reverse CLDR generates reverse lookup tables for low-cardinality CLDR data. Each generated file groups a functional area into objects where each possible CLDR value points back to the default-content locales that use it.

The generated files are created during package installation and are intentionally not checked into git.

Generated Data

The generator currently emits these root-level files:

• numbers.json and numbers.js
• currencies.json and currencies.js
• ca-generic.json and ca-generic.js
• ca-gregorian.json and ca-gregorian.js
• dateFields.json and dateFields.js
• timeZoneNames.json and timeZoneNames.js

Only default-content locales with modern effective CLDR coverage are included. The locale labels come from cldr-core/defaultContent.json; the backing data locale is resolved from cldr-core/availableLocales.json; and the coverage filter comes from cldr-core/coverageLevels.json.

For CLDR 48.2.0, this produces 105 locales, starting with:

[
  "af-ZA",
  "ak-GH",
  "am-ET",
  "ar-001",
  "as-IN",
  "az-Latn-AZ",
  "ba-RU",
  "be-BY",
  "bg-BG",
  "bn-BD",
  "bs-Latn-BA",
  "ca-ES"
]

Example

For example, the CLDR defaultNumberingSystem value is stored per locale in cldr-numbers-full, such as cldr-numbers-full/main/en/numbers.json.

Reverse CLDR aggregates that property across the supported default-content locales. In expanded form, part of numbers.json looks like this:

{
  "numbers": {
    "defaultNumberingSystem": {
      "latn": [
        "af-ZA",
        "ak-GH",
        "am-ET",
        "ar-001",
        "...",
        "zh-Hant-TW",
        "zu-ZA"
      ],
      "beng": [
        "as-IN",
        "bn-BD"
      ],
      "arabext": [
        "fa-IR",
        "ps-AF"
      ],
      "deva": [
        "mr-IN",
        "ne-NP"
      ],
      "mymr": [
        "my-MM"
      ],
      "arab": [
        "sd-Arab-PK"
      ]
    }
  }
}

The checked-in JSON format stores locale sets in a compact de-duplicated form. To expand one of those JSON files for inspection:

node scripts/expandLocales.js numbers.json

The generated JS files expose one function per leaf property. For example:

import { numbers_defaultNumberingSystem } from "reverse-cldr/numbers.js";

const numberingSystems = numbers_defaultNumberingSystem();

Installation And Regeneration

Installing the package runs the generator automatically:

npm install

The install lifecycle calls:

npm run regenerate

You can also run that command manually while developing. It regenerates the root-level .json and .js data files from the installed cldr-* dependencies.

Generated files are listed in .gitignore, so local regeneration does not add data artifacts to source control. If npm scripts are disabled with --ignore-scripts, run npm run regenerate before using the generated lookup files.