Lambda@Edge function for Cloudfront Pretty URLs

cloudfront-pretty-urls.js

/* Public domain project by Cloud Under (https://cloudunder.io).
 * Repository: https://github.com/CloudUnder/lambda-edge-nice-urls
 */

const config = {
  suffix: ".html",
  appendToDirs: "index.html",
  removeTrailingSlash: false,
}

const regexSuffixless = /\/[^/.]+$/ // e.g. "/some/page" but not "/", "/some/" or "/some.jpg"
const regexTrailingSlash = /.+\/$/ // e.g. "/some/" or "/some/page/" but not root "/"

exports.handler = function handler(event, context, callback) {
  const { request } = event.Records[0].cf
  const { uri } = request
  const { suffix, appendToDirs, removeTrailingSlash } = config

  // Append ".html" to origin request
  if (suffix && uri.match(regexSuffixless)) {
    request.uri = uri + suffix
    callback(null, request)
    return
  }

  // Append "index.html" to origin request
  if (appendToDirs && uri.match(regexTrailingSlash)) {
    request.uri = uri + appendToDirs
    callback(null, request)
    return
  }

  // Redirect (301) non-root requests ending in "/" to URI without trailing slash
  if (removeTrailingSlash && uri.match(/.+\/$/)) {
    const response = {
      // body: '',
      // bodyEncoding: 'text',
      headers: {
        location: [
          {
            key: "Location",
            value: uri.slice(0, -1),
          },
        ],
      },
      status: "301",
      statusDescription: "Moved Permanently",
    }
    callback(null, response)
    return
  }

  // If nothing matches, return request unchanged
  callback(null, request)