AWS register IoT thing using promises

register.js

'use strict';

// https://aws.amazon.com/blogs/compute/implementing-a-serverless-aws-iot-backend-with-aws-lambda-and-amazon-dynamodb/

console.log('Loading register function');
var AWS = require('aws-sdk');
AWS.config.region = 'us-east-1';
var iot = new AWS.Iot();
let policyName = 'Policy';
let thingTypeName = 'Type';


module.exports.register = function(event, context, callback) {
    console.log('Received event:', JSON.stringify(event, null, 2));
    let thingName = event.thingName || event.body.thingName;

    var responseData = {};
    var certificateArn;
    iot.createThing({ thingName, thingTypeName }).promise()
        .then((data) => {
            responseData.thing = data;
            return iot.createKeysAndCertificate({ setAsActive: true }).promise();
        })
        .then((certs) => {
            responseData.certificates = certs;
            certificateArn = certs.certificateArn;
            return iot.describeEndpoint({}).promise();
        })
        .then((endpoint) => {
            responseData.endpoint = endpoint;
            return iot.attachPrincipalPolicy({ policyName, principal: certificateArn }).promise();
        })
        .then((data) => {
            responseData.policyAttach = data;
            return iot.attachThingPrincipal({ thingName, principal: certificateArn }).promise()
        })
        .then((data) => {
            responseData.thingAttach = data;
            console.log("created thing " + thingName, responseData);
            callback(null, responseData);
        })
        .catch((err) => {
            console.error(err);
            callback(err)
        });
}