You can use navigator object to detect a browser language preference as below,
var language = navigator.languages && navigator.languages || // Chrome / Firefox
navigator.language || // All browsers
navigator.userLanguage; // IE <= 10
If you like this question & answer and want to contribute, then write your question & answer and email to freewebmentor[@]gmail.com. Your question and answer will appear on FreeWebMentor.com and help other developers.