node_modules/lower-case/lower-case.js

/**
 * Special language-specific overrides.
 *
 * Source: ftp://ftp.unicode.org/Public/UCD/latest/ucd/SpecialCasing.txt
 *
 * @type {Object}
 */
var LANGUAGES = {
  tr: {
    regexp: /\u0130|\u0049|\u0049\u0307/g,
    map: {
      '\u0130': '\u0069',
      '\u0049': '\u0131',
      '\u0049\u0307': '\u0069'
    }
  },
  az: {
    regexp: /[\u0130]/g,
    map: {
      '\u0130': '\u0069',
      '\u0049': '\u0131',
      '\u0049\u0307': '\u0069'
    }
  },
  lt: {
    regexp: /[\u0049\u004A\u012E\u00CC\u00CD\u0128]/g,
    map: {
      '\u0049': '\u0069\u0307',
      '\u004A': '\u006A\u0307',
      '\u012E': '\u012F\u0307',
      '\u00CC': '\u0069\u0307\u0300',
      '\u00CD': '\u0069\u0307\u0301',
      '\u0128': '\u0069\u0307\u0303'
    }
  }
}

/**
 * Lowercase a string.
 *
 * @param  {String} str
 * @return {String}
 */
module.exports = function (str, locale) {
  var lang = LANGUAGES[locale]

  str = str == null ? '' : String(str)

  if (lang) {
    str = str.replace(lang.regexp, function (m) { return lang.map[m] })
  }

  return str.toLowerCase()
}