bvandenbon/redirect-locale.html

## redirect-locale.html
<!DOCTYPE html>
<html>
<body>
<script type="text/javascript">

//////////////
/// CONFIG ///
//////////////

var defaultLocale = 'en';
var routing = {
  "en": 'https://mydomain.com/en',
  "fr": 'https://mydomain.com/fr'
};

var enableLog = true;

/////////////////
/// FUNCTIONS ///
/////////////////

function getBrowserLanguage() {
  if (!navigator) return null;
  if (navigator.languages && navigator.languages.length > 0) return navigator.languages[0];
  if (navigator.userLanguage) return navigator.userLanguage;
  if (navigator.browserLanguage) return navigator.browserLanguage;
  return navigator.language;
}

function getSubPath() {
  var url = window.location.href;
  var domainNameIndex = url.indexOf("//");
  var firstSlashIndex = url.indexOf("/", domainNameIndex + 2);
  if (firstSlashIndex === -1) return null;
  var subPath = url.substring(firstSlashIndex + 1);
  return subPath;
}

function getQueryParam(name) {
  var url = window.location.href;
  name = name.replace(/[\[\]]/g, '\\$&');
  var regex = new RegExp('[?&]' + name + '(=([^&#]*)|&|#|$)'),
      results = regex.exec(url);
  if (!results) return null;
  if (!results[2]) return '';
  return decodeURIComponent(results[2].replace(/\+/g, ' '));
}

function redirectToRoute(locale, subPath) {
  if (enableLog) console.log('matching locale ' + locale + ' ...');
  var route = routing[locale];
  if (route != null) {
    if (enableLog) console.log('will redirect to ' + route);
    if (subPath) {
      if (!route.endsWith('/')) route += '/';
      route += subPath;
      if (enableLog) console.log('full url will be ' + route);
    }
    window.location.replace(route);
    return;
  }

  var parts = locale.split('-');
  if (parts == null || parts.length <= 1) return;

  if (enableLog) console.log("will try to use just the language");
  redirectToRoute(parts[0], subPath);
}

////////////////
/// REDIRECT ///
////////////////

var locale = getQueryParam('locale');
var saveLocale = true;
if (enableLog) console.log('url locale: ' + locale);

if (locale == null) {
  locale = localStorage.getItem('locale');
  if (enableLog) console.log('stored locale: ' + locale);
  if (locale != null) saveLocale = false;
}

if (locale == null) {
  locale = getBrowserLanguage();
  if (enableLog) console.log('browser locale: ' + locale);
}

if (saveLocale === true) {
  if (enableLog) console.log('storing locale: ' + locale);
  localStorage.setItem('locale', locale);
}

if (locale == null) {
  if (enableLog) console.log('will use default ' + defaultLocale);
  locale = defaultLocale;
}

locale = locale.toLowerCase();
var subPath = getSubPath();
redirectToRoute(locale, subPath);
</script>
</body>
</html>
	<!DOCTYPE html>
	<html>
	<body>
	<script type="text/javascript">

	//////////////
	/// CONFIG ///
	//////////////

	var defaultLocale = 'en';
	var routing = {
	"en": 'https://mydomain.com/en',
	"fr": 'https://mydomain.com/fr'
	};

	var enableLog = true;

	/////////////////
	/// FUNCTIONS ///
	/////////////////

	function getBrowserLanguage() {
	if (!navigator) return null;
	if (navigator.languages && navigator.languages.length > 0) return navigator.languages[0];
	if (navigator.userLanguage) return navigator.userLanguage;
	if (navigator.browserLanguage) return navigator.browserLanguage;
	return navigator.language;
	}

	function getSubPath() {
	var url = window.location.href;
	var domainNameIndex = url.indexOf("//");
	var firstSlashIndex = url.indexOf("/", domainNameIndex + 2);
	if (firstSlashIndex === -1) return null;
	var subPath = url.substring(firstSlashIndex + 1);
	return subPath;
	}

	function getQueryParam(name) {
	var url = window.location.href;
	name = name.replace(/[\[\]]/g, '\\$&');
	var regex = new RegExp('[?&]' + name + '(=([^&#]*)\|&\|#\|$)'),
	results = regex.exec(url);
	if (!results) return null;
	if (!results[2]) return '';
	return decodeURIComponent(results[2].replace(/\+/g, ' '));
	}

	function redirectToRoute(locale, subPath) {
	if (enableLog) console.log('matching locale ' + locale + ' ...');
	var route = routing[locale];
	if (route != null) {
	if (enableLog) console.log('will redirect to ' + route);
	if (subPath) {
	if (!route.endsWith('/')) route += '/';
	route += subPath;
	if (enableLog) console.log('full url will be ' + route);
	}
	window.location.replace(route);
	return;
	}

	var parts = locale.split('-');
	if (parts == null \|\| parts.length <= 1) return;

	if (enableLog) console.log("will try to use just the language");
	redirectToRoute(parts[0], subPath);
	}

	////////////////
	/// REDIRECT ///
	////////////////

	var locale = getQueryParam('locale');
	var saveLocale = true;
	if (enableLog) console.log('url locale: ' + locale);

	if (locale == null) {
	locale = localStorage.getItem('locale');
	if (enableLog) console.log('stored locale: ' + locale);
	if (locale != null) saveLocale = false;
	}

	if (locale == null) {
	locale = getBrowserLanguage();
	if (enableLog) console.log('browser locale: ' + locale);
	}

	if (saveLocale === true) {
	if (enableLog) console.log('storing locale: ' + locale);
	localStorage.setItem('locale', locale);
	}

	if (locale == null) {
	if (enableLog) console.log('will use default ' + defaultLocale);
	locale = defaultLocale;
	}

	locale = locale.toLowerCase();
	var subPath = getSubPath();
	redirectToRoute(locale, subPath);
	</script>
	</body>
	</html>