根据用户在 js 中的语言偏好重定向用户？

Question

It is very hard to find any useful code to a working JavaScript Code, that redirects the user to the .html file of their browser language preference. So I have a website which is named index.html and it is in english. And then I have another website in a folder de/index.html which is in german. I want to redirect the user to the german website if he has set his browser language preference to german and let him stay on the english website if he has any other language set as his preference.

|-index.html
|-de
  |-index.html

Answer 1

<script type="text/javascript">
    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];

    if(shortLang === 'de')
        window.location.replace('./' + shortLang + '/index.html');
</script>

If you want to support more languages just update the if statement.