viewer request aws

viewer-request.js

const userAgent = require("useragent");
const path = require("path");

exports.handler = async (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const headers = request.headers;
  const userAgentString =
    headers["user-agent"] && headers["user-agent"][0]
      ? headers["user-agent"][0].value
      : null;
  const agent = userAgent.lookup(userAgentString);

  const browsersToInclude = [
    { browser: "Chrome", version: 23 },
    { browser: "Opera", version: 15 },
    { browser: "Android", version: 53 },
    { browser: "Chrome Mobile", version: 55 },
    { browser: "Opera Mobile", version: 37 },
    { browser: "UC Browser", version: 11 },
    { browser: "Samsung Internet", version: 4 },
  ];

  const supportingBrowser = browsersToInclude.find(
    (browser) =>
      browser.browser === agent.family && agent.major >= browser.version
  );

  if (supportingBrowser) {
    const fileFormat = path.extname(request.uri).replace(".", "");
    request.headers["original-resource-type"] = [
      {
        key: "Original-Resource-Type",
        value: `image/${fileFormat}`,
      },
    ];

    const olduri = request.uri;
    const newuri = olduri.replace(/(\.jpg|\.png|\.jpeg)$/g, ".webp");
    request.uri = newuri;
  }

  return callback(null, request);
};