Purpose

If like me:

you are developping a NodeJS API server which requires internationalization.
you find most i18n libraries too complicated for your needs, or requiring a refactoring of your existing architecture
you find it painful to propagate the request accepted languages in all your application parts

... then this library might be for you.

Read a tutorial to learn how to use this lib here

Framework support

There are almost-one-liners integrations with the following frameworks:

Express => see this sample
Apollo server express => see this sample

How this works

Install it

npm install smartloc --save

Just forget manipulating already translated strings in your code. It is cumbersome, and might leak languages you dont understand in your logs.

Smartloc allows you to declare in your code strings like that:

// recommanded: Explicitely specify a string unique ID
const myString = loc('stringUniqueId')`Hello ${name}, how are you today ?`;

// If you are not affraid of occasionally losing some translations when changing your code,
// then you can use this simpler form:
const myString = loc`Hello ${name}, how are you today ?`;
// => An ID will be autogenerated based on this string hash
//   => you might lose translations when changing the original string in code.

Those will give you an instance of StrLoc interface.

Here is how you can use it:

// build a translatable string
const name = 'world';
const str = loc`Hello ${name}`; // nb: This one will have an auto-generated id.

// Just fake loading translations
setDefaultLocale('en');
addLocale('fr', {
    [str.id]: 'Bonjour {0}',
});

// Use the string without language context (logs, ...)
console.log(str.toString()); // => Hello world
console.log(JSON.stringify({msg: str})); // => {"msg": "Hello world"}

// ... or with language context (when returning a query result, ...)
console.log(withLocales(['it', 'fr'], () => str.toString())); // => Bonjour world
console.log(withLocales(['it', 'fr'], () => JSON.stringify({msg: str})); // => {"msg": "Bonjour world"}

As you might see, the translation is NOT performed when you build the string, but when you actually try to send a result to your end user.

This allows you to build your app without caring about knowing which language your user accepts. The translation will be automatically performed when sending actual json to your user, through a simple middleware (see samples listed in "Framework Support")

Translating your app

Generating/updating translations from code

As an example, if you write your code in english, and you would like to translate your app in French and Deutsch, add the following script to your package.json file:

{
    "scripts": {
        "smartloc": "smartloc collect --format=json --locales=fr-FR,de-DE --defaultLocale=en-US"
    }
}

Once you have written your code (or each time you have changed it), you can run npm run smartloc to create/update your translation files.

nb: The --defaultLocale argument is optional, and will be infered from your code if you explicitly call setDefaultLocale() somewhere.

Loading available translations on server boot

Before serving any request, you must:

Tell smartloc which is the default locale (the one you wrote your translations in)
Load other locales

For 1), this is straightforward: setDefaultLocale('en-US')

To load other locales, you have several options:

Option 1 - Define in code:

import {addLocale} from 'smartloc';

// you could also pass here an object loaded from your database, or whatever
addLocale('fr-FR', {
    mySentenceId: 'Une traduite en français',
});

Option 2 - Load a single given file

import { loadAllLocales } from 'smartloc/node';

await loadAllLocales('/path/to/my-translation.json', true);

nb: The second argument is 'merge'... if false, all previously loaded translations will be cleared. Else, translations will be merged.

Option 3 - Scan a directory for translations

import { loadAllLocales } from 'smartloc/node';

await loadAllLocales('/path/to/dir/to/scan', true);

nb: The second argument is 'merge'... if false, all previously loaded translations will be cleared. Else, translations will be merged.

Supported formats

Smartloc cli implements two translation format through the --format argument

--format=json : JSON translation files
--format=xliff : XLIFF translation files

nb: Smartloc is grouping your translation IDs by category, detected by the first "." in your ID.

Other use cases

The LocStr interface has several implementations:

Smartloc

The default one which is returned when using the loc tag:

return loc`Hello`;

MultiLoc

If you wish to declare all translations directly in your code:

return new MultiLoc({
    en: 'Hello',
    fr: 'Bonjour',
});

SingleLoc

If you wish to declare a string that is the same in all languages, but which is typed as a LocStr:

return new SingleLoc('Typescript');

TransformedLoc

Sometimes, you will want to apply transformations to your final string. You can do that using the .transform() method available on LocStr, which will return you a transformed translatable string.

return loc`Some string wich can contain html`
        .transform(x => escapeHtml(x)); // apply a transformation

Array of LocStr

When you have an array of smartloc strings that you want to join, you can use the LocStringArray class:

const array = new LocStringArray([loc`Hello`, loc`world`]);

const str = array.join(' ').transform(x => x + ' !');

console.log(str.toString('en')); // => Hello world !
console.log(str.toString('fr')); // => Bonjour monde !

Serialization in an untranslated form

Somtimes, you will want to serialize an arbitrary LocStr in its untranslated form (to store a localizable sentence in a DB, for instance).

In this case, you can serialize it like that:

import {loc, MultiLoc, withSerializationContext} from 'smartloc';
const sampleObject = {
    reference: loc('stringId')`Hello {world}`,
    multi: new MultiLoc({ en: 'A string', fr: 'Une chaine' }),
};

// serialize
const serialized = withSerializationContext(() => JSON.stringify(sampleObject));

// store ... nb: it will look like {"reference": "i18n/id:stringId", "multi": {"i18n:fr": "A string", "i18n:en": "Une chaine"}}
storeInDb(serialized);

You can deserialize it back to translatable instance later like that:

import {toLocalizable} from 'smartloc';
const obj = loadFromDb();

// get back a translatable intance
const serializable = toLocalizable(obj);

Cloning

Beware, if you deep-clone an object containing smartloc string instances, you must:

Clone the object prototype
Clone symbol properties

... or you could just ignore cloning smartloc strings altogether (they are immutable anyway): You can detect them using the isLocStr() method and skip them when performing your deep clone.

NB: Of course, if you clone your object using JSON.parse(JSON.stringify(obj)), then you will lose translatability (smartloc strings will be translated as strings in your default language).

oguimbal/smartloc