var lang = new Lang({
    messages: source,
    locale: 'fr',
    fallback: 'zn'
});

{
    "locale1.name": {
        "key1": "value1",
        "key2": "value2",
        // ... and more key-value pairs.
    },
    "locale2.name": {
        "key1": "value1",
        "key2": "value2",
        // ... and more key-value pairs.
    },
    // ... and more locales.
}

var lang = new Lang();
lang.setMessages(source);

var lang = new Lang();

lang.getLocale();
// > "en"

lang.setLocale('fr');
lang.getLocale();
// > "fr"

var lang = new Lang();

lang.setLocale('ht');
lang.getLocale();
// > "ht"

var lang = new Lang();

lang.getFallback();
// > undefined

lang.setFallback('de');
lang.getFallback();
// > "de"

var lang = new Lang({
    messages: {
        'en.greetings': {
            'hi': 'Hi',
            'hello': 'Hello'
        },
        'it.greetings': {
            'hi': 'Salve'
        }
    }
});

lang.setLocale('it');
lang.get('greetings.hello');
// > "greetings.hello"

lang.setFallback('en');
lang.get('greetings.hello');
// > "Hello"

var lang = new Lang({
    messages: {
        'en.greetings': {
            'hi': 'Hi'
        },
        'es.greetings': {
            'hi': 'Hola'
        }
    }
});

lang.has('greetings.hi');
// > true

lang.has('greetings.hi', 'es');
// > true

lang.has('greetings.hello');
// > false

var lang = new Lang({
    messages: {
        'en.greetings': {
            'hi': 'Hi'
        },
        'es.greetings': {
            'hi': 'Hola'
        }
    }
});

lang.get('greetings.hi');
// > "Hi"

lang.get('greetings.hi', {}, 'es');
// > "Hola"

lang.get('greetings.hello');
// > "greetings.hello"

Lang.get('forum/thread.hello');
// > "Hello"

Lang.get('forum/thread.hello', {}, 'es');
// > "Hola"

var lang = new Lang({
    messages: {
        'en.fruits': {
            'apple': 'apple|apples'
        },
        'es.fruits': {
            'apple': 'manzana|manzanas'
        }
    }
});

lang.choice('fruits.apple', 1);
// > "apple"

lang.choice('fruits.apple', 4);
// > "apples"

lang.choice('fruits.apple', 4, {}, 'es');
// > "manzanas"

var lang = new Lang({
    messages: {
        'en.fruits': {
            'apple': '{0} There are none|[1,19] There are some|[20,*] There are many'
        }
    }
});

lang.choice('fruits.apple', 0);   
// > "There are none"

lang.choice('fruits.apple', 1);   
// > "There are some"

lang.choice('fruits.apple', 3);   
// > "There are some"

lang.choice('fruits.apple', 20);   
// > "There are many"

lang.choice('fruits.apple', 22);   
// > "There are many