Today I learned: How to use .env files natively with Node.js

Since Node.js 20 you can specify --env-file arguments.

This may cover most of your needs and we may not need the cumbersome npm config set script-shell "/bin/bash"; source ./.env; prefix to your node commands anymore or even this extra dotenv library you may have dropped into your project's dependencies.
I use "may", because it seems that dotenv features are wider than the native --env-file so beware if you have a sophisticated usage of the dotenv library.

According to Node.js' documentation, --env-file argument...

loads environment variables from a file relative to the current directory, making them available to applications on process.env.

The environment variables which configure Node.js, such as NODE_OPTIONS, are parsed and applied.
If the same variable is defined in the environment and in the file, the value from the environment takes precedence.

You can pass multiple --env-file arguments. Subsequent files override pre-existing variables defined in previous files.An error is thrown if the file does not exist.

Here is an example command, using multiple --env-file arguments:

node --env-file=.env --env-file=.development.env index.js

The --env-file-if-exists flag superclass --env-file in the sense that it first checks for file existence.