dynopromise-client/src/db.js

A client for dynamodb using promises.

const AWS = require('aws-sdk')

// Methods of the AWS DynamoDB DocumentClient to use in promisified db.
const methodsToOverride = ['batchGet', 'batchWrite', 'createSet', 'delete',
'get', 'put', 'query', 'scan', 'update']

module.exports = options => {

	// Give options argument first-priority and fallback to environment variable
	// settings. If nothing is present, an empty object will be based to the
	// DocumentClient constructor and it will fail to initialise.
	const realOptions = options || {}
	if (!realOptions.region && process.env.DYNOPROMISE_AWS_REGION) {
		realOptions.region = process.env.DYNOPROMISE_AWS_REGION
	}
	if (!realOptions.endpoint && process.env.DYNOPROMISE_DYNAMODB_ENDPOINT) {
		realOptions.endpoint = process.env.DYNOPROMISE_DYNAMODB_ENDPOINT
	}
	if (!realOptions.accessKeyId && !realOptions.secretAccessKey &&
		process.env.DYNOPROMISE_AWS_ACCESS_KEY_ID &&
		process.env.DYNOPROMISE_AWS_SECRET_ACCESS_KEY) {
		realOptions.accessKeyId = process.env.DYNOPROMISE_AWS_ACCESS_KEY_ID
		realOptions.secretAccessKey =
			process.env.DYNOPROMISE_AWS_SECRET_ACCESS_KEY
	}

	// Create underlying document client.
	const client = new AWS.DynamoDB.DocumentClient(realOptions)

	// Interface for the promisified db.
	const db = {}

	// Function to bind new db methods to AWS document client methods.
	const callDb = (method, params) => new Promise((resolve, reject) => {
		client[method](params, (err, data) => {
			if (err) {
				return reject(err)
			}
			return resolve(data)
		})
	})

	// Promisfy db API methods.
	for (let method in client) {

		// Only override the methods which are documented.
		if (methodsToOverride.indexOf(method) >= 0) {
			Object.defineProperty(db, method, {
				enumerable: true,
				value: params => callDb(method, params)
			})
		}
	}

	Object.defineProperty(db, 'getDocumentClient', {
		enumerable: true,
		value: () => client
	})

	return db
}