# polyglot.js

- # polyglot.js

- ¶

      (c) 2012-2018 Airbnb, Inc.

      polyglot.js may be freely distributed under the terms of the BSD
      license. For all licensing information, details, and documention:
      http://airbnb.github.com/polyglot.js

  Polyglot.js is an I18n helper library written in JavaScript, made to work both in the browser and in Node. It provides a simple solution for interpolation and pluralization, based off of Airbnb’s experience adding I18n functionality to its Backbone.js and Node apps.

  Polylglot is agnostic to your translation backend. It doesn’t perform any translation; it simply gives you a way to manage translated phrases from your client- or server-side JavaScript application.

      'use strict';

      var forEach = require('for-each');
      var warning = require('warning');
      var has = require('has');
      var trim = require('string.prototype.trim');

      var warn = function warn(message) {
        warning(false, message);
      };

      var replace = String.prototype.replace;
      var split = String.prototype.split;

- ¶

  #### Pluralization methods

  The string that separates the different phrase possibilities.

      var delimiter = '||||';

      var russianPluralGroups = function (n) {
        var end = n % 10;
        if (n !== 11 && end === 1) {
          return 0;
        }
        if (2 <= end && end <= 4 && !(n >= 12 && n <= 14)) {
          return 1;
        }
        return 2;
      };

- ¶

  Mapping from pluralization group plural logic.

      var pluralTypes = {
        arabic: function (n) {

- ¶

  http://www.arabeyes.org/Plural_Forms

          if (n < 3) { return n; }
          var lastTwo = n % 100;
          if (lastTwo >= 3 && lastTwo <= 10) return 3;
          return lastTwo >= 11 ? 4 : 5;
        },
        bosnian_serbian: russianPluralGroups,
        chinese: function () { return 0; },
        croatian: russianPluralGroups,
        french: function (n) { return n > 1 ? 1 : 0; },
        german: function (n) { return n !== 1 ? 1 : 0; },
        russian: russianPluralGroups,
        lithuanian: function (n) {
          if (n % 10 === 1 && n % 100 !== 11) { return 0; }
          return n % 10 >= 2 && n % 10 <= 9 && (n % 100 < 11 || n % 100 > 19) ? 1 : 2;
        },
        czech: function (n) {
          if (n === 1) { return 0; }
          return (n >= 2 && n <= 4) ? 1 : 2;
        },
        polish: function (n) {
          if (n === 1) { return 0; }
          var end = n % 10;
          return 2 <= end && end <= 4 && (n % 100 < 10 || n % 100 >= 20) ? 1 : 2;
        },
        icelandic: function (n) { return (n % 10 !== 1 || n % 100 === 11) ? 1 : 0; },
        slovenian: function (n) {
          var lastTwo = n % 100;
          if (lastTwo === 1) {
            return 0;
          }
          if (lastTwo === 2) {
            return 1;
          }
          if (lastTwo === 3 || lastTwo === 4) {
            return 2;
          }
          return 3;
        }
      };

- ¶

  Mapping from pluralization group to individual language codes/locales. Will look up based on exact match, if not found and it’s a locale will parse the locale for language code, and if that does not exist will default to ‘en’

      var pluralTypeToLanguages = {
        arabic: ['ar'],
        bosnian_serbian: ['bs-Latn-BA', 'bs-Cyrl-BA', 'srl-RS', 'sr-RS'],
        chinese: ['id', 'id-ID', 'ja', 'ko', 'ko-KR', 'lo', 'ms', 'th', 'th-TH', 'zh'],
        croatian: ['hr', 'hr-HR'],
        german: ['fa', 'da', 'de', 'en', 'es', 'fi', 'el', 'he', 'hi-IN', 'hu', 'hu-HU', 'it', 'nl', 'no', 'pt', 'sv', 'tr'],
        french: ['fr', 'tl', 'pt-br'],
        russian: ['ru', 'ru-RU'],
        lithuanian: ['lt'],
        czech: ['cs', 'cs-CZ', 'sk'],
        polish: ['pl'],
        icelandic: ['is'],
        slovenian: ['sl-SL']
      };

      function langToTypeMap(mapping) {
        var ret = {};
        forEach(mapping, function (langs, type) {
          forEach(langs, function (lang) {
            ret[lang] = type;
          });
        });
        return ret;
      }

      function pluralTypeName(locale) {
        var langToPluralType = langToTypeMap(pluralTypeToLanguages);
        return langToPluralType[locale]
          || langToPluralType[split.call(locale, /-/, 1)[0]]
          || langToPluralType.en;
      }

      function pluralTypeIndex(locale, count) {
        return pluralTypes[pluralTypeName(locale)](count);
      }

      function escape(token) {
        return token.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
      }

      function constructTokenRegex(opts) {
        var prefix = (opts && opts.prefix) || '%{';
        var suffix = (opts && opts.suffix) || '}';

        if (prefix === delimiter || suffix === delimiter) {
          throw new RangeError('"' + delimiter + '" token is reserved for pluralization');
        }

        return new RegExp(escape(prefix) + '(.*?)' + escape(suffix), 'g');
      }

      var dollarRegex = /\$/g;
      var dollarBillsYall = '$$';
      var defaultTokenRegex = /%\{(.*?)\}/g;

- ¶

  ### transformPhrase(phrase, substitutions, locale)

  Takes a phrase string and transforms it by choosing the correct plural form and interpolating it.

      transformPhrase('Hello, %{name}!', {name: 'Spike'});
      // "Hello, Spike!"

  The correct plural form is selected if substitutions.smart_count is set. You can pass in a number instead of an Object as `substitutions` as a shortcut for `smart_count`.

      transformPhrase('%{smart_count} new messages |||| 1 new message', {smart_count: 1}, 'en');
      // "1 new message"

      transformPhrase('%{smart_count} new messages |||| 1 new message', {smart_count: 2}, 'en');
      // "2 new messages"

      transformPhrase('%{smart_count} new messages |||| 1 new message', 5, 'en');
      // "5 new messages"

  You should pass in a third argument, the locale, to specify the correct plural type. It defaults to `'en'` with 2 plural forms.

      function transformPhrase(phrase, substitutions, locale, tokenRegex) {
        if (typeof phrase !== 'string') {
          throw new TypeError('Polyglot.transformPhrase expects argument #1 to be string');
        }

        if (substitutions == null) {
          return phrase;
        }

        var result = phrase;
        var interpolationRegex = tokenRegex || defaultTokenRegex;

- ¶

  allow number as a pluralization shortcut

        var options = typeof substitutions === 'number' ? { smart_count: substitutions } : substitutions;

- ¶

  Select plural form: based on a phrase text that contains `n` plural forms separated by `delimiter`, a `locale`, and a `substitutions.smart_count`, choose the correct plural form. This is only done if `count` is set.

        if (options.smart_count != null && result) {
          var texts = split.call(result, delimiter);
          result = trim(texts[pluralTypeIndex(locale || 'en', options.smart_count)] || texts[0]);
        }

- ¶

  Interpolate: Creates a `RegExp` object for each interpolation placeholder.

        result = replace.call(result, interpolationRegex, function (expression, argument) {
          if (!has(options, argument) || options[argument] == null) { return expression; }

- ¶

  Ensure replacement value is escaped to prevent special $-prefixed regex replace tokens.

          return replace.call(options[argument], dollarRegex, dollarBillsYall);
        });

        return result;
      }

- ¶

  ### Polyglot class constructor

      function Polyglot(options) {
        var opts = options || {};
        this.phrases = {};
        this.extend(opts.phrases || {});
        this.currentLocale = opts.locale || 'en';
        var allowMissing = opts.allowMissing ? transformPhrase : null;
        this.onMissingKey = typeof opts.onMissingKey === 'function' ? opts.onMissingKey : allowMissing;
        this.warn = opts.warn || warn;
        this.tokenRegex = constructTokenRegex(opts.interpolation);
      }

- ¶

  ### polyglot.locale([locale])

  Get or set locale. Internally, Polyglot only uses locale for pluralization.

      Polyglot.prototype.locale = function (newLocale) {
        if (newLocale) this.currentLocale = newLocale;
        return this.currentLocale;
      };

- ¶

  ### polyglot.extend(phrases)

  Use `extend` to tell Polyglot how to translate a given key.

      polyglot.extend({
        "hello": "Hello",
        "hello_name": "Hello, %{name}"
      });

  The key can be any string. Feel free to call `extend` multiple times; it will override any phrases with the same key, but leave existing phrases untouched.

  It is also possible to pass nested phrase objects, which get flattened into an object with the nested keys concatenated using dot notation.

      polyglot.extend({
        "nav": {
          "hello": "Hello",
          "hello_name": "Hello, %{name}",
          "sidebar": {
            "welcome": "Welcome"
          }
        }
      });

      console.log(polyglot.phrases);
      // {
      //   'nav.hello': 'Hello',
      //   'nav.hello_name': 'Hello, %{name}',
      //   'nav.sidebar.welcome': 'Welcome'
      // }

  `extend` accepts an optional second argument, `prefix`, which can be used to prefix every key in the phrases object with some string, using dot notation.

      polyglot.extend({
        "hello": "Hello",
        "hello_name": "Hello, %{name}"
      }, "nav");

      console.log(polyglot.phrases);
      // {
      //   'nav.hello': 'Hello',
      //   'nav.hello_name': 'Hello, %{name}'
      // }

  This feature is used internally to support nested phrase objects.

      Polyglot.prototype.extend = function (morePhrases, prefix) {
        forEach(morePhrases, function (phrase, key) {
          var prefixedKey = prefix ? prefix + '.' + key : key;
          if (typeof phrase === 'object') {
            this.extend(phrase, prefixedKey);
          } else {
            this.phrases[prefixedKey] = phrase;
          }
        }, this);
      };

- ¶

  ### polyglot.unset(phrases)

  Use `unset` to selectively remove keys from a polyglot instance.

      polyglot.unset("some_key");
      polyglot.unset({
        "hello": "Hello",
        "hello_name": "Hello, %{name}"
      });

  The unset method can take either a string (for the key), or an object hash with the keys that you would like to unset.

      Polyglot.prototype.unset = function (morePhrases, prefix) {
        if (typeof morePhrases === 'string') {
          delete this.phrases[morePhrases];
        } else {
          forEach(morePhrases, function (phrase, key) {
            var prefixedKey = prefix ? prefix + '.' + key : key;
            if (typeof phrase === 'object') {
              this.unset(phrase, prefixedKey);
            } else {
              delete this.phrases[prefixedKey];
            }
          }, this);
        }
      };

- ¶

  ### polyglot.clear()

  Clears all phrases. Useful for special cases, such as freeing up memory if you have lots of phrases but no longer need to perform any translation. Also used internally by `replace`.

      Polyglot.prototype.clear = function () {
        this.phrases = {};
      };

- ¶

  ### polyglot.replace(phrases)

  Completely replace the existing phrases with a new set of phrases. Normally, just use `extend` to add more phrases, but under certain circumstances, you may want to make sure no old phrases are lying around.

      Polyglot.prototype.replace = function (newPhrases) {
        this.clear();
        this.extend(newPhrases);
      };

- ¶

  ### polyglot.t(key, options)

  The most-used method. Provide a key, and `t` will return the phrase.

      polyglot.t("hello");
      => "Hello"

  The phrase value is provided first by a call to `polyglot.extend()` or `polyglot.replace()`.

  Pass in an object as the second argument to perform interpolation.

      polyglot.t("hello_name", {name: "Spike"});
      => "Hello, Spike"

  If you like, you can provide a default value in case the phrase is missing. Use the special option key “_” to specify a default.

      polyglot.t("i_like_to_write_in_language", {
        _: "I like to write in %{language}.",
        language: "JavaScript"
      });
      => "I like to write in JavaScript."

      Polyglot.prototype.t = function (key, options) {
        var phrase, result;
        var opts = options == null ? {} : options;
        if (typeof this.phrases[key] === 'string') {
          phrase = this.phrases[key];
        } else if (typeof opts._ === 'string') {
          phrase = opts._;
        } else if (this.onMissingKey) {
          var onMissingKey = this.onMissingKey;
          result = onMissingKey(key, opts, this.currentLocale, this.tokenRegex);
        } else {
          this.warn('Missing translation for key: "' + key + '"');
          result = key;
        }
        if (typeof phrase === 'string') {
          result = transformPhrase(phrase, opts, this.currentLocale, this.tokenRegex);
        }
        return result;
      };

- ¶

  ### polyglot.has(key)

  Check if polyglot has a translation for given key

      Polyglot.prototype.has = function (key) {
        return has(this.phrases, key);
      };

- ¶

  export transformPhrase

      Polyglot.transformPhrase = function transform(phrase, substitutions, locale) {
        return transformPhrase(phrase, substitutions, locale);
      };

      module.exports = Polyglot;