Redirect to index.html pages in subdirectories when hosting Static html on S3 and Distributed via cloudfront

CloudfrontRedirectorS3Lambda.js

'use strict';

exports.handler = (event, context, callback) => {
    function getFileExtension(filename) {
  return filename.slice((filename.lastIndexOf(".") - 1 >>> 0) + 2);
}
    // Extract the request from the CloudFront event that is sent to Lambda@Edge 
    var request = event.Records[0].cf.request;
    var extension = getFileExtension(request.uri.substr(request.uri.lastIndexOf('/') + 1));
    console.log(extension);
    // Extract the URI from the request
    var olduri = request.uri.replace('www.','');
    // Match any '/' that occurs at the end of a URI. Replace it with a default index
    var newuri = olduri.replace(/\/$/, '\/index.html');
    if(extension=='' && extension!=='html' && extension!=='htm'){
        newuri = request.uri.replace('www.','') + '/index.html';
    }
    // Log the URI as received by CloudFront and the new URI to be used to fetch from origin
    console.log("Old URI: " + olduri);
    console.log("New URI: " + newuri);
    
    // Replace the received URI with the URI that includes the index page
    request.uri = newuri;
    
    // Return to CloudFront
    return callback(null, request);

};