Specifying dependencies

You specify the dependencies for your Node.js app by declaring them in the package.json file.

For example, if you want to specify Lodash as a dependency, your package.json file might look as follows:

{
  "dependencies": {
    "lodash": "^4.0.1"
  }
}

During deployment, the Node.js runtime automatically installs all dependencies declared in your package.json file. By default, the npm install command is used, however Yarn and Pnpm package managers are also supported:

Yarn: If a yarn.lock file exists, the yarn install --production command is used instead.
Pnpm: If a pnpm-lock.yaml file exists, the pnpm install command is used instead.

Note that you must ensure that the yarn.lock or pnpm-lock.yaml file is not specified in the skip_files section of your app.yaml file.

By default, App Engine caches fetched dependencies to reduce build times. To install an uncached version of the dependency, use the command:

gcloud app deploy --no-cache

Support and limitations for the package.json file in the standard environment:

You can use any Linux-compatible Node.js package with App Engine, including packages that require native (C) extensions.
If the engines field is specified in your package.json, you must define a compatible Node.js version.
All dependencies that you define under the devDependencies field are ignored and do not get installed for your app in App Engine.
The start script should be lightweight and exclude build steps for the best performance because the script runs each time a new instance of your application is created.

Private dependencies with Artifact Registry

If your app uses a private npm module, you can use an Artifact Registry Node.js package repository to host private dependencies. When deploying your app, the build process automatically generates Artifact Registry credentials for the Cloud Build service account so you won't need to generate additional credentials. To include private dependencies, list the Artifact Registry repository and configure settings for authenticating with the registry in your .npmrc file in the app directory. For example:

@SCOPE:registry=https://REGION_ID-npm.pkg.dev/PROJECT_ID/REPOSITORY_NAME
//REGION_ID-npm.pkg.dev/PROJECT_ID/REPOSITORY_NAME:always-auth=true

Note that this approach also works for Yarn v1 package manager. If you are using Yarn v2 or higher, list the Artifact Registry repository and configure settings for authenticating with the registry in your .yarnrc.yml file in the app directory. For example:

npmScopes:
  SCOPE:
    npmRegistryServer: https://REGION_ID-npm.pkg.dev/PROJECT_ID/REPOSITORY_NAME
    npmAlwaysAuth: true

Afterwards, include your packages in the package.json file. For example:

{
  "dependencies": {
    " @SCOPE/my-package": "^1.0.0"
  }
}

Installing a web framework

You'll need to use a web framework to enable your app to serve web requests. You can use any Node.js web framework including the following:

To use a particular web framework, such as Express.js, add the framework to your package.json file:

Using npm:
```
npm install --save express
```
Using yarn:
```
yarn add express
```
Using pnpm:
```
pnpm add express
```

For example, the resulting package.json file might look as follows:

{
  "dependencies": {
    "lodash": "^4.0.1",
    "express": "^4.16.2"
  }
}

Installing the Cloud Client Libraries

The Cloud Client Libraries for Node.js is the idiomatic way for Node.js developers to integrate with Google Cloud services, such as Firestore in Datastore mode (Datastore) and Cloud Storage.

To install the Node.js client library for Cloud Storage:

Install the Cloud Client Libraries locally by using a package manager:
- To use npm, run:
```
npm install --save @google-cloud/storage
```
- To use yarn, run:
```
yarn add @google-cloud/storage
```
- To use pnpm, run:
```
pnpm add @google-cloud/storage
```
Set up authentication. You can configure the Cloud Client Libraries for Node.js to handle authentication automatically.
Use the Node.js client library for Cloud Storage reference to implement support for the Cloud Storage service in your app.