Introduction

NestJS is a progressive web framework used to build a back-end application using TypeScript.
I've been using it to build my project, BrawlDB, and found it harder than expected to deploy on Beanstalk.
This led me to writing this guide, hopefully it will facilitate your journey through the deployment!

Local workflow

Running the application locally is quite easy: npm start
This runs ts-node on the src/main.ts file, which launches the server on the default nest/express port, 3000.
ts-node lets us execute TypeScript files without manually compiling them with tsc first, which accelerates the development cycle.

Application port

The first thing we need to change in our code is the port on which our application listens.
Beanstalk, and many other production enviroment, expects us to use the PORT enviroment variable. This is not the case on the default template yet, therefore we need to update the src/main.ts file to listen on the correct port.
This is as simple as using process.env.PORT || 3000 instead of the previously hardcoded 3000.
This will use the PORT variable if it exists, and fallback to 3000 if it has not been set.

Typescript

On AWS Beanstalk's NodeJS environment, the dev dependencies are not installed. This is normal as the --only=production flag is given to the npm install command, in order to prevent unnecessary code from being installed.
This means that ts-node will not be installed, and therefore npm start will fail.

Fortunately, compiling typescript is easy! NestJS's starter application provides us with a default working tsconfig.json, therefore all we need to do is run tsc on a terminal with TypeScript installed!
Running tsc will build all of our typescript files into the dist folder. The application entrypoint will therefore be dist/src/main.js.

Missing files

While the dist folder will contain the compiled Javascript files, it is not enough to run and deploy the application.
In order to know the dependencies to install, NodeJS requires the package.json file.
In my project, I store the configuration files in the config/config.json file, which also were not copied into the dist folder as they are not ts.
In order to deploy the application, we therefore need to copy all non-typescript configuration files, including package.json, to the dist folder.

Beanstalk configuration

Finally, once we're ready to deploy everything on Beanstalk, there is one setting we need to change.
As the default npm start will not work with our folders, considering there is no main.ts nor ts-node installed, we need to tell Beanstalk to run node src/main.js.
This setting is Node command, which can be found under Container Options in the beanstalk configuration screen.

Once the environment has launched, the application should be up and running on the given beanstalk URL!

Conclusion

Once you've understood the previous steps to deploy your NestJS application, updating and redeploying it is easy.
Hopefully this guide did help you with this process, and you'll keep on making awesome applications!