Embedded Lambda custom resource for getting an EB Environment's ELB's CanonicalHostedZoneId

index.js

var AWS = require('aws-sdk');
var response = require('cfn-response');
exports.handler = function(event, context) {
  console.log('REQUEST RECEIVED: %j', event);
  if (event.RequestType == 'Delete') {
    response.send(event, context, response.SUCCESS);
    return;
  }
  var environmentId = event.ResourceProperties.EnvironmentId;
  var responseData = {};
  if (environmentId) {
    var Beanstalk = new AWS.ElasticBeanstalk();
    Beanstalk.describeStacks({
      EnvironmentIds: [
        environmentId
      ]
    }, function(err, ebEnv) {
      var ELB = new AWS.ELB();
      var ELBName = null;
      if (err) {
        responseData = {
          Error: 'ElasticBeanstalk.describeEnvironments call failed'
        };
        console.log(responseData.Error + ':\n', err);
        response.send(event, context, response.FAILED, responseData);
      } else {
        ELBName = ebEnv && ebEnv.EnvironmentResources && ebEnv.EnvironmentResources.LoadBalancers && ebEnv.EnvironmentResources.LoadBalancers[0] && ebEnv.EnvironmentResources.LoadBalancers[0].Name;

        if (!ELBName) {
          responseData = {
            Error: 'ELBName not present'
          };
          console.log(responseData.Error + ':\n', err);
          response.send(event, context, response.FAILED, responseData);
        } else {
          console.log('Got ELBName: ' + ELBName);
          console.log('Accessing ELB description...');

          ELB.describeLoadBalancers({
            LoadBalancerNames: [
              ELBName
            ]
          }, function(err, elbDesc) {
            var CanonicalHostedZoneId = null;
            if (err) {
              responseData = {
                Error: 'ELB.describeLoadBalancers call failed'
              };
              console.log(responseData.Error + ':\n', err);
              response.send(event, context, response.FAILED, responseData);
            } else {
              CanonicalHostedZoneId = elbDesc && elbDesc.LoadBalancerDescriptions && elbDesc.LoadBalancerDescriptions[0] && elbDesc.LoadBalancerDescriptions[0].CanonicalHostedZoneNameID;

              if (!CanonicalHostedZoneId) {
                responseData = {
                  Error: 'CanonicalHostedZoneId not present'
                };
                console.log(responseData.Error + ':\n', err);
                response.send(event, context, response.FAILED, responseData);
              } else {
                console.log('Got CanonicalHostedZoneId: ' + CanonicalHostedZoneId);
                response.send(event, context, response.SUCCESS, {
                  HostedZoneId: CanonicalHostedZoneId
                });
              }
            }
          });
        }
      }
    });
  } else {
    responseData = {Error: 'Environment id not specified'};
    console.log(responseData.Error);
    response.send(event, context, response.FAILED, responseData);
  }
};