Implementation of locale specific funtionality for js-joda, providing function not implemented in js-joda core

Especially this implements patterns elements to print and parse locale specific dates

also see examples in examples folder

Since the process described below requires a lot of setup and internal knowledge, we provide prebuilt sets of locales as separate npm packages. So for ease of use you may want to install the corresponding @js-joda/locale_<locale> package. The current list of available prebuilt locales is:

• de (i.e. de-*)
• de-DE
• en (i.e. en-*)
• en-US
• es (i.e. es-*)
• fr (i.e. fr-*)
• fr-FR
• hi (i.e. hi-*)
• it (i.e. it-*)
• it-IT
• ja (i.e. js-*)
• ja-jp
• ko (i.e. ko-*)
• ro (i.e. ro-*)
• ru (i.e. ru-*)
• sv (i.e. sv-*)
• sv-SE
• zh (i.e. zh-*)

this list could be extended relatively easily if needed, as long as data is available in cldr-data

with these packages, no further steps are needed to build the cldr-data.

Install required packages using npm

    npm install @js-joda/core
    npm install @js-joda/timezone
    npm install @js-joda/locale_en-us

To enable @js-joda/locale you will only need to require it, requiring it automatically registers the locale extensions in the base js-joda Note: the Locale class is exported by @js-joda/locale_<locale> so in order to use it, you will need to extract it from there.

Since @js-joda/locale requires @js-joda/timezone it will also need to be provided, as shown in the following examples

const { DateTimeFormatter, ZonedDateTime, ZoneId } = require('@js-joda/core');
require('@js-joda/timezone');
const { Locale } = require('@js-joda/locale_en-us');

const zdt = ZonedDateTime.of(2016, 1, 1, 0, 0, 0, 0, ZoneId.of('Europe/Berlin'));
console.log('en_US formatted string:', 
    zdt.format(DateTimeFormatter
            .ofPattern('eeee MMMM dd yyyy GGGG, hh:mm:ss a zzzz, \'Week \' ww, \'Quarter \' QQQ')
            .withLocale(Locale.US)));

this will output en_US formatted string: Friday January 01 2016 Anno Domini, 12:00:00 AM Central European Time, Week 01, Quarter Q1

also see examples/usage_node.js or examples/usage_node_build.js

It is also possible to not use the prebuilt packages by using @js-joda/locale directly.

The implementation requires cldr data provided by the cldr-data package and uses cldrjs to load the data. This is necessary to display and parse locale specific data, e.g DayOfWeek or Month Names.

The cldr data is a peer dependency of this package, meaning it must be provided/npm installed by users of @js-joda/locale

Since the complete cldr-data package can be quite large, the examples and documentation further below show ways to dynamically load or reduce the amount of data needed.

The implementation of @js-joda/locale also requires @js-joda/timezone package e.g. to parse and output timezone names and offsets

    npm install @js-joda/core
    npm install @js-joda/timezone
    npm install cldr-data
    npm install cldrjs
    npm install @js-joda/locale

With cldr-data installed, you can use any custom Locale supported by the https://cldr.unicode.org/ project as shown in the example below. Find the full list of supported locales here https://github.com/unicode-org/cldr/tree/main/common/main

const { DateTimeFormatter, ZonedDateTime, ZoneId } = require('@js-joda/core');
require('@js-joda/timezone');
const { Locale } = require('@js-joda/locale');

const zdt = ZonedDateTime.of(2016, 1, 1, 0, 0, 0, 0, ZoneId.of('Europe/Berlin'));
const localeThai = new Locale('th', 'TH', 'th');

console.log('th_TH formatted string:', 
    zdt.format(DateTimeFormatter
            .ofPattern('eeee MMMM dd yyyy GGGG, hh:mm:ss a zzzz, \'Week \' ww, \'Quarter \' QQQ')
            .withLocale(localeThai)));

This will output th_TH formatted string: วันศุกร์ มกราคม 01 2016 คริสต์ศักราช, 12:00:00 ก่อนเที่ยง เวลายุโรปกลาง, Week 01, Quarter ไตรมาส 1

import { DateTimeFormatter, ZonedDateTime, ZoneId } from '@js-joda/core';
import '@js-joda/timezone';
import { Locale } from '.@js-joda/locale_en-us';

const zdt = ZonedDateTime.of(2016, 1, 1, 0, 0, 0, 0, ZoneId.of('Europe/Berlin'));
console.log('en_US formatted string:', zdt.format(DateTimeFormatter.ofPattern('eeee MMMM dd yyyy GGGG, hh:mm:ss a zzzz, \'Week \' ww, \'Quarter \' QQQ').withLocale(Locale.US)));

also see the example

• using @js-joda umd or iife builds
• or using requirejs to load
• might also be possible with the bower version of cldr-data

see the example requirejs and example custom iife build

Update: The following documentation is partly outdated, because we changed from webpack to rollup.

rollup-examples.config.js is a good starting point to see how we bundle packages and minimize package size with rollup.

Since the cldr-data files can still be quite large, it is possible to only load the files needed for your application

Also possible would be to use webpack to reduce the overall size of the cldr-data (similar approaches should work with different packaging tools than webpack).

So the following tips are just one way to get the general idea on how to reduce the size of needed cldr-data, we use this for our karma testing setup in karma.conf.js and to build the prebuilt locale packages

In package.json file define which parts of cldr-data to download and install

(for more information see the cldr-data-npm docs)

...
"cldr-data-coverage": "core",
"cldr-data-urls-filter": "(cldr-core|cldr-numbers-modern|cldr-dates-modern)"
...

(data-coverage core only downloads data for the most popular languages / locales, while the urls-filter defines which parts of cldr-data are required for @js-joda/locale to work)

In e.g. webpack.config.js, define which parts/locales of the cldr-data files should end up in the final package

You can for example use the null-loader to disable loading cldr-data except for the absolutely required parts/locales

use: [{ loader: 'null-loader' }],
resource: {
    // don't load everything in cldr-data
    test: path.resolve(__dirname, 'node_modules/cldr-data'),
    // except the actual data we need (supplemental and de, en, fr locales from main)
    exclude: [
        path.resolve(__dirname, 'node_modules/cldr-data/main/de'),
        path.resolve(__dirname, 'node_modules/cldr-data/main/en'),
        path.resolve(__dirname, 'node_modules/cldr-data/main/fr'),
        path.resolve(__dirname, 'node_modules/cldr-data/supplemental'),
    ],
}

or (as we do for our prebuilt packages) use the CldrDataIgnorePlugin, provided in utils/CldrDataIgnorePlugin.js

    "plugins": [
        new CldrDataIgnorePlugin(modulesDir, locales)),
    ]

where modulesDir is the absolute path to node_modules and locales is an array of locales to use as they can be defined for the prebuilt packages. This will only load the absolutely required files for @js-joda/locale, it is what we use internally for the prebuilt packages and to build packages for our karma tests as well.

Depending on your usecase it might also be necessary to define a "faked" cldr-data module that loads the cldr-data files, this is necessary at least if the code needs to run in the browser since the cldr-data load uses modules not available in browser (e.g. fs)

    // add cldr-data load workaround
    resolve = {
        alias: {
            'cldr-data$': path.resolve(__dirname, 'test/utils/karma_cldrData.js'),
        }
    };

These should be the minimum required parts for @js-joda/locale

see the karma.conf.js

provides methods for the following pattern letters of the DateTimeFormatterBuilder and DateTimeFormatter classes of js-joda

Localized Text

• a for am/pm of day
• G for era
• q/Q for localized quarter of year

Zone Text

• z for time zone name
• Z for localized ZoneOffsets
• O for localized ZoneOffsets

Week Information

• w for week-of-year
• W for week-of-month
• Y for week-based-year
• e for localized day-of-week
• c for localized day-of-week

some of these are only partially localized, e.g. Q only if three or more Q are used, one or two Q also work with plain @js-joda/core without using @js-joda/locale

• @js-joda/locale is released under the BSD 3-clause license
• The author of joda time and the lead architect of the JSR-310 is Stephen Colebourne.