Detect browser language in javascript (utilizing lodash/fp)

detectBrowserLanguage.js

// These window.navigator contain language information
// 1. languages -> Array of preferred languages (eg ["en-US", "zh-CN", "ja-JP"]) Firefox^32, Chrome^32
// 2. language  -> Preferred language as String (eg "en-US") Firefox^5, IE^11, Safari, 
//                 Chrome sends Browser UI language
const browserLanguagePropertyKeys = ['languages', 'language'];
const availableLanguages = ['en', 'es'];

const detectedLocale = _.flow(
  _.pick(browserLanguagePropertyKeys), // Get only language properties
  _.values, // Get values of the properties
  _.flatten, // Flatten all arrays
  _.compact, // Remove undefined values
  _.map(lang => lang.substr(0, 2)), //Shorten strings to use two chars (en-US -> en)
  _.find(lang => _.includes(lang)(availableLanguages)) //Returns first language matched in available languages
)(self.navigator);

const locale = detectedLocale || 'en'; // If no locale is detected, fallback to 'en'