npm gives you two groups to specify dependencies (i.e. dev and prod). In the real world, we have multiple dependency environments (e.g. test, build, production, development).

Let’s say you run webpack on heroku to build your app. There are 2 options:

1. Set heroku config:set NPM_CONFIG_PRODUCTION=false to install all dependencies (including testing dependencies)
2. Put your build dependencies in dependencies (i.e. production environment)

With group-dependencies, you can declare your build dependencies in a separate property, buildDependencies, and install only those packages as needed, by adding to "scripts": { "heroku-postbuild": deps install build" } to your package.json.

npm install group-dependencies

First, add a new dependencies group to package.json:

{
  ...
  "devDependencies": {
    "intercept-stdout": "^0.1.2",
    "jest": "^20.0.4",
    "strip-color": "^0.1.0"
  },
  // our new group representing testing dependencies
  "testDependencies": [
    "jest"
  ]
  ...
}

Now you can install only the dependencies for this new group:

# This will install jest@^20.0.4:
deps install test

# Install dependencies in the named group
deps install [GROUP_NAME]

Any item added to the [GROUP_NAME]Dependencies property will be installed with deps install [GROUP_NAME]. If a matching package is found in devDependencies, that version will be installed.

// Here's the part that matters.
"buildDependencies": [
  "webpack",
  "@babel/preset-env"
]

The decision to use this strategy, with an array, was made so that we can leverage a few things.

1. In your development enviroment, let npm manage installing your dev dependencies.
2. You only need to manage package versions in one location, reducing the overhead.