This post is written by Dan Fox, Principal Specialist Solutions Architect, Serverless.

You can now develop AWS Lambda functions using the Node.js 16 runtime. This version is in active LTS status and considered ready for general use. To use this new version, specify a runtime parameter value of nodejs16.x when creating or updating functions or by using the appropriate container base image.

The Node.js 16 runtime includes support for ES modules and top-level await that was added to the Node.js 14 runtime in January 2022. This is especially useful when used with Provisioned Concurrency to reduce cold start times.

This runtime version is supported by functions running on either Arm-based AWS Graviton2 processors or x86-based processors. Using the Graviton2 processor architecture option allows you to get up to 34% better price performance.

We recognize that customers have been waiting for some time for this runtime release. We hear your feedback and plan to release the next Node.js runtime version in a timelier manner.

AWS SDK for JavaScript

The Node.js 16 managed runtimes and container base images bundle the AWS JavaScript SDK version 2. Using the bundled SDK is convenient for a few use cases. For example, developers writing short functions via the Lambda console or inline functions via CloudFormation templates may find it useful to reference the bundled SDK.

In general, however, including the SDK in the function’s deployment package is good practice. Including the SDK pins a function to a specific minor version of the package, insulating code from SDK API or behavior changes. To include the SDK, refer to the SDK package and version in the dependency object of the package.json file. Use a package manager like npm or yarn to download and install the library locally before building and deploying your deployment package to the AWS Cloud.

Customers who take this route should consider using the JavaScript SDK, version 3. This version of the SDK contains modular packages. This can reduce the size of your deployment package, improving your function’s performance. Additionally, version 3 contains improved TypeScript compatibility, and using it will maximize compatibility with future runtime releases.

Language updates

With this release, Lambda customers can take advantage of new Node.js 16 language features, including:

Prebuilt binaries for Apple Silicon

Node.js 16 is the first runtime release to ship prebuilt binaries for Apple Silicon. Customers using M1 processors in Apple computers may now develop Lambda functions locally using this runtime version.

Stable timers promises API

The timers promises API offers timer functions that return promise objects, improving the functionality for managing timers. This feature is available for both ES modules and CommonJS.

You may designate your function as an ES module by changing the file name extension of your handler file to .mjs, or by specifying “type” as “module” in the function’s package.json file. Learn more about using Node.js ES modules in AWS Lambda.

 // index.mjs import { setTimeout } from 'timers/promises'; export async function handler() { await setTimeout(2000); return; }

RegExp match indices

The RegExp match indices feature allows developers to get an array of the start and end indices of the captured string in a regular expression. Use the “/d” flag in your regular expression to access this feature.

 // handler.js exports.lambdaHandler = async () => { const matcher = /(AWS )(Lambda)/d.exec('AWS Lambda'); console.log("match: " + matcher.indices[0]) // 0,10 console.log("first capture group: " + matcher.indices[1]) // 0,4 console.log("second capture group: " + matcher.indices[2]) // 4,10 }

Working with TypeScript

Many developers using Node.js runtimes in Lambda develop their code using TypeScript. To better support TypeScript developers, we have recently published new documentation on using TypeScript with Lambda, and added beta TypeScript support to the AWS SAM CLI.

We are also working on a TypeScript version of Lambda PowerTools. This is a suite of utilities for Lambda developers to simplify the adoption of best practices, such as tracing, structured logging, custom metrics, and more. Currently, AWS Lambda Powertools for TypeScript is in beta developer preview.

Runtime updates

To help keep Lambda functions secure, AWS will update Node.js 16 with all minor updates released by the Node.js community when using the zip archive format. For Lambda functions packaged as a container image, pull, rebuild, and deploy the latest base image from DockerHub or the Amazon ECR Public Gallery.

Amazon Linux 2

The Node.js 16 managed runtime, like Node.js 14, Java 11, and Python 3.9, is based on an Amazon Linux 2 execution environment. Amazon Linux 2 provides a secure, stable, and high-performance execution environment to develop and run cloud and enterprise applications.

Conclusion

Lambda now supports Node.js 16. Get started building with Node.js 16 by specifying a runtime parameter value of nodejs16.x when creating your Lambda functions using the zip archive packaging format.

You can also build Lambda functions in Node.js 16 by deploying your function code as a container image using the Node.js 16 AWS base image for Lambda. You can read about the Node.js programming model in the AWS Lambda documentation to learn more about writing functions in Node.js 16.

For existing Node.js functions, review your code for compatibility with Node.js 16 including deprecations, then migrate to the new runtime by changing the function’s runtime configuration to nodejs16.x.

For more serverless learning resources, visit Serverless Land.