Load Configuration Into the Enviroment in Node.js

When writing CLI tools, command-line flags are the best way to temporarily change the behavior of the program for a single execution, such as enabling verbose mode or selecting an output format.

However, CLI tools often also need a more persistent type of configuration and a safer way to store sensitive values, such as API keys, tokens, or secrets, without typing them on every command or leaking them into your shell history.

These values are usually stored in the shell environment, or in .env files whose contents are loaded and injected into the environment at startup.

📚 The shell environment, often abbreviated env, is a collection of variables in the form of name-value pairs.

For example:

HOME=/home/razvan/projectsPATH=/usr/bin:/bin:/usr/sbin:/sbin/USER=razvan

Access environment variables

In Node.js, the environment variables available in the shell session the script was launched from are exposed through the global process.env object:

process.env.ENV_VAR

⚠️ While the process.env object can be modified by the script, such modifications won't be reflected outside of the Node.js process.