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2.1.1 • Public • Published

Command-line MessageFormat Compiler

Parses and compiles the input JSON and .properties file(s) of MessageFormat strings into a JS module of corresponding hierarchical functions.


npm install messageformat@next messageformat-cli

messageformat is a peer dependency of messageformat-cli, and needs to be installed separately.


npx messageformat [options] [input]


./node_modules/.bin/messageformat [options] [input]

input should consist of one or more files or directories, unless defined in a configuration file. Directories are recursively scanned for .json and .properties files. With multiple input files, shared parts of the start of their paths are dropped out of the generated module's structure.


In addition to defining options on the command line, options may also be set in the "messageformat" object in your package.json file, or in a messageformat.rc.json configuration file, using the long-form option names as keys. Input files and directories may also be given as an "include" array in a configuration file. Command-line options override configuration files.

-l lc, --locale=lc

The locale(s) lc to include; if multiple, first is default and others are selected by matching message key. If not set or empty, path keys matching any locale code will set the active locale, starting with a default en locale.

-n ns, --namespace=ns

By default, output is an ES6 module with a default export; set ns to support other environments. If ns does not contain a ., the output follows an UMD pattern. For CommonJS module output, use --namespace=module.exports.

-o of, --outfile=of

Write output to the file of. If unspecified or -, prints to stdout.


Set of characters by which the file path is split into output object keys. [default: ._/ or ._\ depending on platform]


By default, messageformat throws an error when a statement uses a non-numerical key that will never be matched as a pluralization category for the current locale. Use this argument to disable the validation and allow unused plural keys. [default: false]


Add an /* eslint-disable */ comment as the first line of the output, to silence ESLint warnings. [default: false]


Array or comma-separated list of file extensions to parse as source files. [default: ['.json', '.properties']]


Simplify the output object structure, by dropping intermediate keys when those keys are shared across all objects at that level, in addition to the default filtering-out of shared keys at the root of the object. [default: false]


With messages/strings.json, compile it into a node.js module using the default English locale:

npx messageformat messages/strings.json > messages/en.js

With messages/en.json and messages/fr.json, combine both into an ES6-compatible module, with the top-level keys en and fr containing functions that each use the correct language's pluralization rules:

npx messageformat --locale=en,fr messages/ > messages.js

Note: The locale option could be left out here if is known that the data does not include any 2-3 letter keys matching other locales.

Same, but with this configuration in package.json:

  "messageformat": {
    "locale": ["en", "fr"],
    "include": [
    "outfile": "messages.js"
  "scripts": {
    "build:messages": "messageformat"
npm run build:messages


npm i messageformat-cli

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