Return pre-rendered html files for non-supported browsers

lambda-edge-prerender.js

const whitelist = ['chrome', 'crios', 'firefox', 'fxios', 'googlebot'];

const isSupportedBrowser = uas => {
  if (uas && Array.isArray(uas) && uas.length > 0) {
    return uas.some(ua =>
      whitelist.some(w => ua.value.toLowerCase().includes(w))
    );
  }
  return false;
};

exports.handler = (event, context, callback) => {
  const request = event.Records[0].cf.request;
  const { headers } = request;

  if (!isSupportedBrowser(headers['user-agent'])) {
    if (
      !request.uri ||
      request.uri === '/' ||
      request.uri.includes('index.html')
    ) {
      request.uri = '/index.static.html';
    } else {
      request.uri += '.static.html';
    }
  }
  callback(null, request);
};