javascript localization library

en.js

// English translations
{
  "en" : {
    "error" : {
      "fetching"    : "An error occurred while attempting to fetch %{what}",
      "notified"    : "We've been notified about this issue, and we'll take a look at it shortly."
    },

    "confirm" : {
      "delete"  : "Are you sure you want to delete this highlight?"
    }
  }
}

I18n.js

var i18n = (function(){
  // this copy of the i18n object is for the constructor
  var i18n = function(){
    // privleged vars
    var _locales = {};

    // public vars
    this.locale = 'en';

    // priviledged methods that can access local variables;
    this.locales    = function(){ return _locales; };
    this.localeList = function(){
      var ll = [];
      for(var l in _locales){ ll.push(l); }
      return ll;
    };

    this.addLocale  = function(){
      // make sure the second argument isn't a callback
      if((arguments.length >= 2) && (arguments[1].constructor == Object)){
        _locales[arguments[0]] = arguments[1];

        // make sure there's a callback and that the callback is a function
        if(arguments[2] && (arguments[2].constructor == Function)){
          return arguments[2](arguments[1]);
        }
      }else{
        var path      = arguments[0],
            pathParts = path.split('/'),
            locale    = pathParts[pathParts.length - 1].split('.')[0],
            self      = this,
            callback  = arguments[1];

        // this timestamp is because android can cache this junk w/o telling us
        // we probably need a more robust way that doesn't include ALWAYS pull a new copy
        var timestamp = new Date().getTime();
        if(path.indexOf('?') < 0){ path += '?' + timestamp; }
        else{ path += '&' + timestamp; }

        $.getJSON(path, function(data){
          self.addLocale(locale, data[locale], callback);
        });
      }
    };

  };

  // public methods

  // really no good reason to put these on the prototype object instead of just declaring them in the constructor, but...
  // I feel like putting them here right now.
  //
  // for the translate method, I'm still trying to decide if it's worth
  // having the option to raise an error if the translation or locale can't be found
  i18n.prototype.translate = function(key){
    var thisLocale  = this.locales()[this.locale];

    var replacements  = arguments[1] || {},
        tokenizer     = /(%%\{[^\}]+\}|%\{[^\}]+\})/,
        interpolation = /(%)?(%\{([^\}]+)\})/,
        tokens;

    // get out of here if we can't find the locale
    if(!thisLocale){ return 'locale not found: ' + this.locale; }

    var parts = key.split('.'),
        found = thisLocale;

    for (var i=0; i < parts.length; i++) {
      found = found[parts[i]];
      if(!found){ return 'translation not found: ' + key; }
    };

    // we only handle strings
    if(found.constructor != String){ return 'translation not found: ' + key; }

    // now that we've found it, begin interpolation...
    tokens = found.split(tokenizer);

    var t;
    for (var i = tokens.length - 1; i >= 0; i--){
      if( t = tokens[i].match(interpolation) ){
        // need to see if the last element of the tokens array matches any of the replacements
        // that were passed in and change the value in the tokens array if it does
        if(replacements && replacements[t[t.length-1]]){
          tokens[i] = replacements[t[t.length-1]];
        }
      }
    };

    return tokens.join('');
  };

  // alias the translate function
  i18n.prototype.t = i18n.prototype.translate;

  return new i18n();
}());

pt.js

// Portugues translations
{
  "pt" : {
    "error" : {
      "fetching"    : "Ocorreu um erro ao tentar capturar %{what}",
      "notified"    : "Sabemos da ocorrncia deste problema e o resolveremos em breve.",
    },

    "confirm" : {
      "delete"  : "Tem certeza de que deseja excluir este?",
    }
  }
}

USAGE.js

// USAGE

// English
i18n.addLocale('/javascripts/locales/en.js');
// Portuguese
i18n.addLocale('/javascripts/locales/pt.js');

// set the current locale
i18n.locale = 'en';

// translate a string:
i18n.t('confirm.delete') //=> "Are you sure you want to delete this?"

// translate a string with a dynamic value
i18n.t('error.fetching', {what: 'stuff'}) //=> An error occurred while attempting to fetch stuff