JavaScript for detecting browser language preference [duplicate]

Answer 1

let lang = window.navigator.languages ? window.navigator.languages[0] : null;
    lang = lang || window.navigator.language || window.navigator.browserLanguage || window.navigator.userLanguage;

let shortLang = lang;
if (shortLang.indexOf('-') !== -1)
    shortLang = shortLang.split('-')[0];

if (shortLang.indexOf('_') !== -1)
    shortLang = shortLang.split('_')[0];

console.log(lang, shortLang);

I only needed the primary component for my needs, but you can easily just use the full string. Works with latest Chrome, Firefox, Safari and IE10+.