Optimizing request URI for CloudFront with CloudFront Functions (CF2) that has HUGO site that deployed to a S3 bucket as origin.

cf2_for_hugo.js

function handler(event) {
  var host = '<REPLARE_TO_YOUR_HOST>'; // e.g. https://michimani.net
  var request = event.request;
  var requestUri = request.uri;

  // do not anything when requesting to top page
  if (requestUri == '' || requestUri == '/') {
    return request;
  }

  // redirect to URI end with '/' if URL end with 'index.html' or not '/'
  if (requestUri.match(/((page|post|posts|tags|categories|archives|about)(\/.*[^\/])?|\/index\.html)$/)) {
    var redirectUrl = host + requestUri.replace('/index.html', '') + '/';
    var response = {
      statusCode: 301,
      statusDescription: 'Found',
      headers: {
        location: {
            value: redirectUrl
        }
      }
    }

    // response to viewer
    return response;
  }

  // complete `index.html` for requests to origin
  var actualUri = requestUri.replace(/\/$/, '\/index.html');
  request.uri = actualUri;

  // request to origin
  return request;
}