Assuming you’ve already installed Node.js and (Java or GraalVM), create a directory to hold your application, and make that your working directory.

mkdir myapp
cd myapp

Use the npm init command to create a package.json file for your application. For more information on how package.json works, see Specifics of npm’s package.json handling.

npm init

This command prompts you for a number of things, such as the name and version of your application. For now, you can simply hit RETURN to accept the defaults for most of them, with the following exception:

entry point: (index.js)

Enter app.js, or whatever you want the name of the main file to be. If you want it to be index.js, hit RETURN to accept the suggested default file name.

Update the package.json to accomodate the ES4X scripts in the myapp directory. For example:

npx es4x-cli init

Now install @vertx/core and optionally @vertx/web and @vertx/unit dependencies by adding them to the package.json or running the command:

npm install @vertx/unit --save-dev
npm install @vertx/core --save-prod
npm install @vertx/web --save-prod

npm install

As this moment there should be a minimal package.json.