Messy code but working, connect to Amazon SP-API

SP-API.js

/*
  This code is full of antipatterns and bad practices!
  It's not intended to be used as is but rather as inspiration on how to connect to SP-API,
  the only reason I publish this is because I couldn't find anything better online, NOT because its well written code!
*/


// make sure to fill out all the following:

// info from seller central developer page
const refreshToken = "";
const clientId = "";
const clientSecret = "";


// info from the IAM user
const AccessKey = "";
const SecretKey = "";


// info from the IAM role
const RoleArn = '';











const fetch = require("node-fetch");
const URLSearchParams = require("url").URLSearchParams;
const aws4 = require("aws4");
const https = require("https");
const aws = require("aws-sdk");


aws.config = new aws.Config();
aws.config.credentials = new aws.Credentials(AccessKey, SecretKey);
aws.config.getCredentials(function (err) {
	if (err) {
		console.log(err);
		throw new Error("can't login to AWS");
	} else {
		console.log("Connected to AWS");
	}
});
const sts = new aws.STS();

async function getCrossAccountCredentials () {
	return new Promise((resolve, reject) => {
		const params = {
			RoleArn,
			RoleSessionName: `postmanSpApi`
		};
		sts.assumeRole(params, (err, data) => {
			if (err) reject(err);
			else {
				resolve({
					accessKeyId: data.Credentials.AccessKeyId,
					secretAccessKey: data.Credentials.SecretAccessKey,
					sessionToken: data.Credentials.SessionToken,
				});
			}
		});
	});
}

function getAccessToken2() {
	let formData = new URLSearchParams();
	formData.append("grant_type", "refresh_token");
	formData.append("refresh_token", refreshToken);
	formData.append("client_id", clientId);
	formData.append("client_secret", clientSecret);

	return fetch("https://api.amazon.com/auth/o2/token", {
		method: "POST",
		body: formData,
	})
		.then(res => res.json())
		.then(res => {
			return res.access_token;
		});
}

function getOrders3(accessKeyId, secretAccessKey, sessionToken, accessToken) {
	return new Promise((resolve, reject) => {
		const xAmzDate = new Date().toISOString().replace(/-|:/g, "").substring(0, 15) + "Z";

		var opts = {
			host: 'sellingpartnerapi-na.amazon.com',
			path: '/orders/v0/orders?MarketplaceIds=ATVPDKIKX0DER&CreatedAfter=2010-01-01T05%3A00%3A00.000Z',
			service: 'execute-api',
			region: 'us-east-1',
			signQuery: false,
			headers: {
				'x-amz-access-token': accessToken,
				"x-amz-date": xAmzDate,
				"x-amz-security-token": sessionToken,
			},
		}

		aws4.sign(opts, { accessKeyId, secretAccessKey })

		const req = https.request(opts, (res) => {	
			var body = '';
			res.on('data', function(chunk) {
				body += chunk;
			});
			res.on('end', function() {
				resolve(JSON.parse(body));
			});
		});
		console.log(req);

		req.on('error', (e) => {
			console.error(e);
		});

		req.end()
	});
}



(async () => {
	let info = {
		accessKeyId: undefined,
		secretAccessKey: undefined,
		sessionToken: undefined,
		accessToken: undefined,
	}

	info = await getCrossAccountCredentials();
	info.accessToken = await getAccessToken2();

	let orders = await getOrders3(info.accessKeyId, info.secretAccessKey, info.sessionToken, info.accessToken);
	console.log(orders);

})();