message: Refactor articles
diff: * @param {string} article
  */
  function _switch (article) {
  - if (article === 'a') {
  - return 'an'
  - }
  - return 'a'
  + return article === 'a' ? 'an' : 'a'
  }
  /**
  * @param {boolean} [caseSensitive]
  */
  function addOverride (article, word, caseSensitive) {
  - let msg
  if (State.length > 0) {
  // must be called in story JS or StoryInit, as the override map isn't stateful
  - msg = 'cannot add article override -> needs to be run in StoryInit special passage or earlier'
  - console.error(msg)
  - return msg
  + const message = 'cannot add article override -> needs to be run in StoryInit special passage or earlier'
  + console.error(message)
  + return message
  }
  // check args
  if (!word || typeof word !== 'string') {
  - msg = 'cannot add article override -> invalid word'
  - console.error(msg)
  - return msg
  + const message = 'cannot add article override -> invalid word'
  + console.error(message)
  + return message
  }
  if (article && typeof article === 'string') {
  // clean up article
  article = article.toLowerCase().trim()
  }
  if (!_validArticles.includes(article)) {
  - msg = 'cannot add article override -> invalid article, must be "a" or "an"'
  - console.error(msg)
  - return msg
  + const message = 'cannot add article override -> invalid article, must be "a" or "an"'
  + console.error(message)
  + return message
  }
  // clean up phrase
  word = word.trim()
  - if (caseSensitive) {
  - _overrides.set(word, {
  - article,
  - caseSensitive: !!caseSensitive
  - })
  - } else {
  - _overrides.set(word.toLowerCase(), {
  + _overrides.set(caseSensitive ? word : word.toLowerCase(), {
  article,
  caseSensitive: !!caseSensitive
  })
  }
  - }
  /**
  * @param {string} word
  * @param {string} word
  */
  function _checkVowels (word) {
  - let article
  // select the article based on vowels
  - if (_vowels.test(word.first())) {
  - article = 'an'
  - } else {
  - article = 'a'
  - }
  + const article = _vowels.test(word.first()) ? 'an' : 'a'
  +
  // check for irregular words, then acronyms
  return _isDefaultIrregular(word, article) || _isAcronym(word, article) || article
  }
  