VueI18n = function VueI18n (options) {
  var this$1 = this;
  if ( options === void 0 ) options = {};

  // Auto install if it is not done yet and `window` has `Vue`.
  // To allow users to avoid auto-installation in some cases,
  // this code should be placed here. See #290
  /* istanbul ignore if */
  if (!Vue && typeof window !== 'undefined' && window.Vue) {
    install(window.Vue);
  }

  var locale = options.locale || 'en-US';
  var fallbackLocale = options.fallbackLocale === false
    ? false
    : options.fallbackLocale || 'en-US';
  var messages = options.messages || {};
  var dateTimeFormats = options.dateTimeFormats || {};
  var numberFormats = options.numberFormats || {};

  this._vm = null;
  this._formatter = options.formatter || defaultFormatter;
  this._modifiers = options.modifiers || {};
  this._missing = options.missing || null;
  this._root = options.root || null;
  this._sync = options.sync === undefined ? true : !!options.sync;
  this._fallbackRoot = options.fallbackRoot === undefined
    ? true
    : !!options.fallbackRoot;
  this._formatFallbackMessages = options.formatFallbackMessages === undefined
    ? false
    : !!options.formatFallbackMessages;
  this._silentTranslationWarn = options.silentTranslationWarn === undefined
    ? false
    : options.silentTranslationWarn;
  this._silentFallbackWarn = options.silentFallbackWarn === undefined
    ? false
    : !!options.silentFallbackWarn;
  this._dateTimeFormatters = {};
  this._numberFormatters = {};
  this._path = new I18nPath();
  this._dataListeners = new Set();
  this._componentInstanceCreatedListener = options.componentInstanceCreatedListener || null;
  this._preserveDirectiveContent = options.preserveDirectiveContent === undefined
    ? false
    : !!options.preserveDirectiveContent;
  this.pluralizationRules = options.pluralizationRules || {};
  this._warnHtmlInMessage = options.warnHtmlInMessage || 'off';
  this._postTranslation = options.postTranslation || null;
  this._escapeParameterHtml = options.escapeParameterHtml || false;

  /**
   * @param choice {number} a choice index given by the input to $tc: `$tc('path.to.rule', choiceIndex)`
   * @param choicesLength {number} an overall amount of available choices
   * @returns a final choice index
  */
  this.getChoiceIndex = function (choice, choicesLength) {
    var thisPrototype = Object.getPrototypeOf(this$1);
    if (thisPrototype && thisPrototype.getChoiceIndex) {
      var prototypeGetChoiceIndex = (thisPrototype.getChoiceIndex);
      return (prototypeGetChoiceIndex).call(this$1, choice, choicesLength)
    }

    // Default (old) getChoiceIndex implementation - english-compatible
    var defaultImpl = function (_choice, _choicesLength) {
      _choice = Math.abs(_choice);

      if (_choicesLength === 2) {
        return _choice
          ? _choice > 1
            ? 1
            : 0
          : 1
      }

      return _choice ? Math.min(_choice, 2) : 0
    };

    if (this$1.locale in this$1.pluralizationRules) {
      return this$1.pluralizationRules[this$1.locale].apply(this$1, [choice, choicesLength])
    } else {
      return defaultImpl(choice, choicesLength)
    }
  };


  this._exist = function (message, key) {
    if (!message || !key) { return false }
    if (!isNull(this$1._path.getPathValue(message, key))) { return true }
    // fallback for flat key
    if (message[key]) { return true }
    return false
  };

  if (this._warnHtmlInMessage === 'warn' || this._warnHtmlInMessage === 'error') {
    Object.keys(messages).forEach(function (locale) {
      this$1._checkLocaleMessage(locale, this$1._warnHtmlInMessage, messages[locale]);
    });
  }

  this._initVM({
    locale: locale,
    fallbackLocale: fallbackLocale,
    messages: messages,
    dateTimeFormats: dateTimeFormats,
    numberFormats: numberFormats
  });
}
Get path value from path string