Use NPM commands to configure

This encourages best practces & avoids errors running npm install later

doc/user/packages/npm_registry/index.md

@@ -73,20 +73,20 @@ If you have 2FA enabled, you need to use a [personal access token](../../profile
 ### Authenticating with an OAuth token
 
 To authenticate with an [OAuth token](../../../api/oauth2.md#resource-owner-password-credentials-flow)
-or [personal access token](../../profile/personal_access_tokens.md), add a corresponding section to your `.npmrc` file:
+or [personal access token](../../profile/personal_access_tokens.md), set your NPM configuration:
 
-```ini
-; Set URL for your scoped packages.
-; For example package with name `@foo/bar` will use this URL for download
-@foo:registry=https://gitlab.com/api/v4/packages/npm/
+```bash
+# Set URL for your scoped packages.
+# For example package with name `@foo/bar` will use this URL for download
+npm config set @foo:registry https://gitlab.com/api/v4/packages/npm/
 
-; Add the token for the scoped packages URL. This will allow you to download
-; `@foo/` packages from private projects.
-//gitlab.com/api/v4/packages/npm/:_authToken=<your_token>
+# Add the token for the scoped packages URL. This will allow you to download
+# `@foo/` packages from private projects.
+npm config set '//gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken' "<your_token>"
 
-; Add token for uploading to the registry. Replace <your_project_id>
-; with the project you want your package to be uploaded to.
-//gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken=<your_token>
+# Add token for uploading to the registry. Replace <your_project_id>
+# with the project you want your package to be uploaded to.
+npm config set '//gitlab.com/api/v4/packages/npm/:_authToken' "<your_token>"
 ```
 
 Replace `<your_project_id>` with your project ID which can be found on the home page
@@ -103,13 +103,11 @@ If you encounter an error message with [Yarn](https://yarnpkg.com/en/), see the
 
 ### Using variables to avoid hard-coding auth token values
 
-To avoid hard-coding the `authToken` value, you may use a variables in its place.
-In your `.npmrc` file, you would add:
+To avoid hard-coding the `authToken` value, you may use a variables in its place:
 
-```ini
-@foo:registry=https://gitlab.com/api/v4/packages/npm/
-//gitlab.com/api/v4/packages/npm/:_authToken=${NPM_TOKEN}
-//gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken=${NPM_TOKEN}
+```bash
+npm config set '//gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken' "${NPM_TOKEN}"
+npm config set '//gitlab.com/api/v4/packages/npm/:_authToken' "${NPM_TOKEN}"
 ```
 
 Then, you could run `npm publish` either locally or via GitLab CI/CD:
@@ -227,6 +225,14 @@ And the `.npmrc` file should look like:
 @foo:registry=https://gitlab.com/api/v4/packages/npm/
 ```
 
+### `npm install` returns `Error: Failed to replace env in config: ${NPM_TOKEN}`
+
+You do not need a token to run `npm install` unless your project is private (the token is only required to publish). If the `.npmrc` file was checked in with a reference to `$NPM_TOKEN`, you can remove it. If you prefer to leave the reference in, you'll need to set a value prior to running `npm install` or set the value using [GitLab environment variables](./../../../ci/variables/README.md):
+
+```bash
+NPM_TOKEN=<your_token> npm install
+```
+
 ## NPM dependencies metadata
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/11867) in GitLab Premium 12.6.