handler.js

const path = require('path');
const { STATUS_CODES } = require('http');

exports.rewriteHandler = (evt, ctx, cb) => {
  const { request } = evt.Records[0].cf;
  const htmlExtRegex = /(.*)\.html?$/;
  if (htmlExtRegex.test(request.uri)) {
    const uri = request.uri.replace(htmlExtRegex, '$1');
    return cb(null, redirect(uri));
  }
  if (!path.extname(request.uri)) {
    request.uri = '/index.html';
  }
  cb(null, request);
};
function redirect(to) {
  return {
    status: '301',
    statusDescription: STATUS_CODES['301'],
    headers: {
      location: [{ key: 'Location', value: to }],
    },
  };
}