lambda function to redirect based of browser's language.js

exports.handler =  (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const headers = request.headers;
  if(request.uri == '/') {
    if (typeof headers['accept-language'] !== 'undefined') {
      const supportedLanguages = headers['accept-language'][0].value;
      console.log('Supported languages:', supportedLanguages);
      if(supportedLanguages.startsWith('en')){
        callback(null, redirect('/en/index.html'));
      } else if(supportedLanguages.startsWith('ja')){
        callback(null, redirect('/ja/index.html'));
      } else if(supportedLanguages.startsWith('fr')){
        callback(null, redirect('/fr/'));
      } else if(supportedLanguages.startsWith('it')){
        callback(null, redirect('/it/'));
      } else if(supportedLanguages.startsWith('pl')){
        callback(null, redirect('/pl-PL/'));
      } else {
        callback(null, redirect('/ja/index.html'));
      }
    } else {
      callback(null, redirect('/ja/index.html'));
    }
  } else {
    callback(null, request);
  }
};

function redirect (to) {
  return {
    status: '301',
    statusDescription: 'redirect to browser language',
    headers: {
      location: [{ key: 'Location', value: to }]
    }
  };
}