Write i18n messages inline. Transpile translations.
npm install format-message --save
adds the library to node_modules
. You can then use it as follows:
var formatMessage = require('format-message');
var message = formatMessage('Hello { place }!', { place:'World' });
You can configure your translations at runtime (typical for server-side use), or transpile your code for better performance in repeated use on the client.
format-message
relies on the ECMAScript Internationalization API 1.0 (Intl
) for formatting number
, date
, and time
arguments. If you are in an environment missing these (like node <= 0.12, IE < 11, or Safari) you'll want to use a polyfill. Otherwise format-message
falls back on toLocaleString
methods, which are most likely just aliases for toString
.
The ICU Message Format is a great format for user-visible strings, and includes simple placeholders, number and date placeholders, and selecting among submessages for gender and plural arguments. The format is used in apis in C++, PHP, and Java.
format-message
provides a way to write your default (often English) messages as literals in your source, and then scrape out the default patterns and transpile your source with fast inline code for formatting the translated message patterns.
This relies on message-format for parsing and formatting ICU messages, and babel for transpiling the source code.
See message-format for supported ICU formats.
See the ICU site and message-format for details on how to escape special characters in your messages.
format-message
supports plurals for all CLDR languages. Locale-aware formatting of number, date, and time are delegated to the Intl
apis, and select is the same across all locales. You don't need to load any extra files for particular locales for format-message
itself.
var formatMessage = require('format-message')
// or
import formatMessage from 'format-message'
formatMessage(pattern[, args[, locales]])
Translate and format the message with the given pattern and arguments.
Parameters
pattern
is a properly formatted ICU Message Format pattern. A poorly formatted pattern will cause anError
to be thrown.- The pattern is used as a key into the
translate
function you provide in configuration, and is also used as the fallback if no translation is returned, ortranslate
has not been configured - If
pattern
is not a string literal, the function cannot be transpiled at build time.
- The pattern is used as a key into the
args
is an object containing the values to replace placeholders with. Required if the pattern contains placeholders.locales
is an optional string with a BCP 47 language tag, or an array of such strings.- The locales are also passed into the
translate
function and indicate the desired destination language. - If
locales
is not a string literal, the function cannot be transpiled at build time.
- The locales are also passed into the
formatMessage.setup(options)
Configure formatMessage
behavior for subsequent calls. This should be called before any code that uses formatMessage
.
Parameters
options
is an object containing the following config values:cache
is whether message, number, and date formatters are cached. Defaults totrue
locale
is the default locale to use when no locale is passed toformatMessage
. Defaults to"en"
.translate(pattern, locales)
is a function to translate messages. It should return the pattern translated for the specified locale.pattern
is the message pattern to translate.locale
is a string with a BCP 47 language tag, or an array of such strings.
formatMessage.translate(pattern[, locales])
Use the currently configured translate
to get the locale-specific pattern. Note that this can also be linted, extracted, and inlined if the pattern
is a literal.
Parameters
pattern
is a properly formatted ICU Message Format pattern.locales
is an optional string with a BCP 47 language tag, or an array of such strings.- If not specified, the currently configured
locale
will be used.
- If not specified, the currently configured
formatMessage.number
, formatMessage.date
, and formatMessage.time
are used internally and are not intended for external use. Because these appear in the transpiled code, transpiling does not remove the need to properly define formatMessage
through require
or import
.
The examples provide sample transpiler output. This output is not meant to be 100% exact, but to give a general idea of what the transpiler does.
formatMessage('My Collections')
// transpiles to translated literal
"Minhas Coleções"
formatMessage('Welcome, {name}!', { name: userName });
// messages with simple placeholders transpiles to concatenated strings
"Bem Vindo, " + userName + "!" // Bem Vindo, Bob!
formatMessage('{ n, number, percent }', { n:0.1 });
// transpiles to just the number call
formatMessage.number("en", 0.1, "percent") // "10%"
formatMessage('{ shorty, date, short }', { shorty:new Date() });
// transpiles to just the date call
formatMessage.date("en", new Date(), "short") // "1/1/15"
formatMessage('You took {n,number} pictures since {d,date} {d,time}', { n:4000, d:new Date() });
// transpiles to a function call, with the function defined at the top level
$$_you_took_n_number_pictures_123456({ n:4000, d:new Date() })
...
function $$_you_took_n_number_pictures_123456(args) {
return "You took " + formatMessage.number("en", args["n"]) + " pictures since " + formatMessage.date("en", args["d"]) + " " + formatMessage.time("en", args["d"])
} // "You took 4,000 pictures since Jan 1, 2015 9:33:04 AM"
import formatMessage from 'format-message'
// using a template string for multiline, no interpolation
let formatMessage(`On { date, date, short } {name} ate {
numBananas, plural,
=0 {no bananas}
=1 {a banana}
=2 {a pair of bananas}
other {# bananas}
} {
gender, select,
male {at his house.}
female {at her house.}
other {at their house.}
}`, {
date: new Date(),
name: 'Curious George',
gender: 'male',
numBananas: 27
})
// transpiles to a function call, with the function defined at the top level
$$_on_date_date_short_name_ate_123456({ n:4000, d:new Date() })
...
function $$_on_date_date_short_name_ate_123456(args) {
return ...
}
// en-US: "On 1/1/15 Curious George ate 27 bananas at his house."
- Calls with no placeholders in the message become string literals.
- Calls with no
plural
,select
, orselectordinal
in the message, and an object literal with variables or literals for property values become concatentated strings and variables.
All other cases result in a function call, with the function declaration somewhere at the top level of the file.
All of the command line tools will look for require
ing or import
ing format-message
in your source files to determine the local name of the formatMessage
function. Then they will either check for problems, extract the original message patterns, or replace the call as follows:
find message patterns in files and verify there are no obvious problems
-h, --help output usage information
-n, --function-name [name] find function calls with this name [formatMessage]
--no-auto disables auto-detecting the function name from import or require calls
-k, --key-type [type] derived key from source pattern literal|normalized|underscored|underscored_crc32 [underscored_crc32]
-t, --translations [path] location of the JSON file with message translations, if specified, translations are also checked for errors
-f, --filename [filename] filename to use when reading from stdin - this will be used in source-maps, errors etc [stdin]
lint the src js files, with __
as the function name used instead of formatMessage
format-message lint -n __ src/**/*.js
lint the src js files and translations
format-message lint -t i18n/pt-BR.json src/**/*.js
find and list all message patterns in files
-h, --help output usage information
-n, --function-name [name] find function calls with this name [formatMessage]
--no-auto disables auto-detecting the function name from import or require calls
-k, --key-type [type] derived key from source pattern (literal | normalized | underscored | underscored_crc32) [underscored_crc32]
-l, --locale [locale] BCP 47 language tags specifying the source default locale [en]
-o, --out-file [out] write messages JSON object to this file instead of to stdout
extract patterns from src js files, dump json to stdout
. This can be helpful to get familiar with how --key-type
and --locale
change the json output.
format-message extract src/**/*.js
extract patterns from stdin
, dump to file.
someTranspiler src/*.js | format-message extract -o locales/en.json
find and replace message pattern calls in files with translations
-h, --help output usage information
-n, --function-name [name] find function calls with this name [formatMessage]
--no-auto disables auto-detecting the function name from import or require calls
-k, --key-type [type] derived key from source pattern (literal | normalized | underscored | underscored_crc32) [underscored_crc32]
-l, --locale [locale] BCP 47 language tags specifying the target locale [en]
-t, --translations [path] location of the JSON file with message translations
-e, --missing-translation [behavior] behavior when --translations is specified, but a translated pattern is missing (error | warning | ignore) [error]
-m, --missing-replacement [pattern] pattern to inline when a translated pattern is missing, defaults to the source pattern
-i, --source-maps-inline append sourceMappingURL comment to bottom of code
-s, --source-maps save source map alongside the compiled code
-f, --filename [filename] filename to use when reading from stdin - this will be used in source-maps, errors etc [stdin]
-o, --out-file [out] compile all input files into a single file
-d, --out-dir [out] compile an input directory of modules into an output directory
-r, --root [path] remove root path for source filename in output directory [cwd]
create locale-specific client bundles with source maps
format-message inline src/**/*.js -s -l de -t translations.json -o dist/bundle.de.js
format-message inline src/**/*.js -s -l en -t translations.json -o dist/bundle.en.js
format-message inline src/**/*.js -s -l es -t translations.json -o dist/bundle.es.js
format-message inline src/**/*.js -s -l pt -t translations.json -o dist/bundle.pt.js
...
inline without translating multiple files that used var __ = require('format-message')
format-message inline -d dist -r src -n __ src/*.js lib/*.js component/**/*.js
This software is free to use under the MIT license. See the LICENSE-MIT file for license text and copyright information.