CloudFront Function to redirect other domains

cloudfront-function-domain-redirect.js

var domain = 'example.com';

function handler(event) {
  // console.log('Event:\n' + JSON.stringify(event, null, 2));
  // console.log('Request:\n' + JSON.stringify(event.request, null, 2));
  var request = event.request;
  var uriQs = request.uri + (!!Object.keys(request.querystring).length ? '?' + querystringText(request.querystring) : '');
  var url = request.headers.host.value + uriQs;

  if (request.headers.host.value === domain) {
    console.log(`Passthrough: ${url}`);
    return request;
  }

  var location = 'https://' + domain + uriQs;
  console.log(`Redirect: ${url} to ${location}`);
  return {
    statusCode: 301,
    statusDescription: 'Moved Permanently',
    headers: {
      'location': {
        value: location,
      },
    },
  };
};

function querystringText(querystring) {
  var text = '';
  for (var key in querystring) {
    if (text !== '') {
      text += '&';
    }
    text += encodeURIComponent(key) + '=' + encodeURIComponent(querystring[key].value);
  }
  return text;
}