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node-dotenv-extended

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A module for loading .env files and optionally loading defaults and a schema for validating all values are present.

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# dotenv-extended

Extended `.env` loading with defaults and schema validation.

## Supported Node Versions

- Node `20.x`
- Node `22.x`
- Node `24.x`

I've been a big fan of the [dotenv] for a quite some time (in fact, this library uses [dotenv] under the hood for the `.env` file parsing). However, while working on some bigger projects, we realized that the managing of the `.env` files became a bit of a chore. As the files changed in the development environments, it became a tedious manual process to compare and figure out what needed to be added or removed in the other environments.

This library solves some of these issues by introducing the concept of 3 files which are used together to provide environment-specific variables, default values and a validation schema:

### `.env`

The environment specific file (not committed to source control). This file will have sensitive information such as usernames, passwords, api keys, etc. These would be specific to each environment and should not be committed to source control. The format is a series of key-value pairs. Any line starting with `#` or `;` are commented out and ignored.

```
# .env file
MONGO_HOST=localhost
MONGO_DATABASE=TestDB
MONGO_USER=dbusername
MONGO_PASS=dbpassword!
```

### `.env.defaults`

Common configuration defaults across all environments (commited to source control). This contains overall app configuration values that would be common across environments. The `.env.defaults` file is loaded first and then the `.env` file is loaded and will overwrite any values from the `.env.defaults` file. Format is identical to the `.env` file.

### `.env.schema`

Defines a schema of what variables _should_ be defined in the combination of `.env` and `.env.defaults`. Optionally, you can have the library throw an error if all values are not configured or if there are extra values that shouldn't be there.

The `.env.schema` file should only have the name of the variable and the `=` without any value:

```
MONGO_HOST=
MONGO_DATABASE=
MONGO_USER=
MONGO_PASS=
```

Additionally `.env.schema` can include regular expressions; see [below](#load-files-with-erroronregex) for how to configure the library to throw an error upon failed regex validation.

I have tried to stay as compatible as possible with the [dotenv] library but there are some differences.

## Installation

```bash
npm i --save dotenv-extended
```

## Development

```bash
npm run check
```

`npm run check` runs linting, formatting checks, and tests.

Use individual commands only when needed:

```bash
npm run build
npm run lint
npm run format
npm run test:unit
npm test
```

## Usage

As early as possible in your main script:

```javascript
require('dotenv-extended').load();
```

Or if you prefer import syntax:

```javascript
import dotEnvExtended from 'dotenv-extended';
dotEnvExtended.load();
```

Create a `.env` file in the root directory of your project. Add environment-specific variables on new lines in the form of `NAME=VALUE`.

For example:

```
MONGO_HOST=localhost
MONGO_DATABASE=TestDB
MONGO_USER=dbusername
MONGO_PASS=dbpassword!
```

`process.env` now has the keys and values you defined in your `.env` file.

```javascript
mongoose.connect('mongodb://' + process.env.MONGO_HOST + '/' + process.env.MONGO_DATABASE, {
    user: process.env.MONGO_USER,
    pass: process.env.MONGO_PASS,
});
```

### Load Configs from command line

You may also load the `.env` files from the command line. Add in the require `dotenv-extended/config` along with any of the options that the `load` method takes prefixed with `dotenv_config_`. e.g.:

```bash
node -r dotenv-extended/config your_script.js
```

Or to specify load options:

```bash
node -r dotenv-extended/config your_script.js dotenv_config_path=./env/.env dotenv_config_defaults=./env/.env.defaults
```

`dotenv_config_*` values are normalized to the same option names as `load()`, supporting both snake_case and kebab-case style keys.

### Load Environment Variables and pass to non-NodeJS script

New in 2.0.0, is a feature inspired by [cross-env](https://www.npmjs.com/package/cross-env) to allow you to load environment variables from your `.env` files and then pass them into a non-NodeJS script such as a shell script. This can simplify the process of maintaining variables used in both your Node app and other scripts. To use this command line executable, you will either need to install globally with the `-g` flag, or install `dotenv-extended` in your project and reference it from your npm scripts.

The package exposes two equivalent CLI commands:

- `dotenv-extended` (original)
- `dee` (short alias)

Install Globally:

```bash
npm install -g dotenv-extended
```

Now call your shell scripts through `dee` (this uses the defaults):

```bash
dee ./myshellscript.sh --whatever-flags-my-script-takes
```

Configure `dee` (or `dotenv-extended`) by passing any of the dotenv-extended options before your command. Preceed each option with two dashes `--`:

```bash
dee --path=/path/to/.env --defaults=/path/to/.env.defaults --errorOnMissing=true ./myshellscript.sh --whatever-flags-my-script-takes
```

`--path` and `--defaults` also support comma-separated layered files:

```bash
dee \
  --defaults=./env/.env.defaults.base,./env/.env.defaults.local \
  --path=./env/.env.base,./env/.env.development \
  ./myshellscript.sh
```

You can also print the merged dotenv configuration (without full `process.env`) instead of executing a command:

```bash
dee --print
dee --print=dotenv
```

- `--print` outputs JSON
- `--print=dotenv` outputs `KEY=value` lines

The following are the flags you can pass to the `dotenv-extended` cli with their default values. these options detailed later in this document:

```bash
--encoding=utf8
--silent=true
--path=.env
--defaults=.env.defaults
--schema=.env.schema
--errorOnMissing=false     # or --error-on-missing=false
--errorOnExtra=false       # or --error-on-extra=false
--errorOnRegex=false       # or --error-on-regex=false
--includeProcessEnv=false  # or --include-process-env=false
--assignToProcessEnv=true  # or --assign-to-process-env=true
--overrideProcessEnv=false # or --override-process-env=true
```

## Options

Defaults are shown below:

```javascript
require('dotenv-extended').load({
    encoding: 'utf8',
    silent: true,
    path: '.env',
    defaults: '.env.defaults',
    schema: '.env.schema',
    schemaExtends: undefined, // string | string[]
    errorOnMissing: false,
    errorOnExtra: false,
    errorOnRegex: false,
    errorOnMissingFiles: false,
    includeProcessEnv: false,
    returnSchemaOnly: false,
    assignToProcessEnv: true,
    overrideProcessEnv: false,
});
```

### Configure via Environment Variables (New in 2.8.0)

You may also set the configuration values via environment variables loaded from `process.env` shown below with defaults:

```
DOTENV_CONFIG_ENCODING=utf8
DOTENV_CONFIG_SILENT=true
DOTENV_CONFIG_PATH=.env
DOTENV_CONFIG_DEFAULTS=.env.defaults
DOTENV_CONFIG_SCHEMA=.env.schema
DOTENV_CONFIG_SCHEMA_EXTENDS=
DOTENV_CONFIG_ERROR_ON_MISSING=false
DOTENV_CONFIG_ERROR_ON_EXTRA=false
DOTENV_CONFIG_ERROR_ON_REGEX=false
DOTENV_CONFIG_ERROR_ON_MISSING_FILES=false
DOTENV_CONFIG_INCLUDE_PROCESS_ENV=false
DOTENV_CONFIG_RETURN_SCHEMA_ONLY=false
DOTENV_CONFIG_ASSIGN_TO_PROCESS_ENV=true
DOTENV_CONFIG_OVERRIDE_PROCESS_ENV=false
```

`DOTENV_CONFIG_PATH`, `DOTENV_CONFIG_DEFAULTS`, and `DOTENV_CONFIG_SCHEMA_EXTENDS` can each be set to comma-separated file paths for layered loading.

The `load()` function always returns an object containing the variables loaded from the `.env` and `.env.defaults` files. By default the returned object does not contain the properties held in `process.env` but rather only the ones that are loaded from the `.env` and `.env.defaults` files.

```javascript
const myConfig = require('dotenv-extended').load();
```

### encoding (_default: utf8_)

Sets the encoding of the `.env` files

### silent (_default: true_)

Sets whether a log message is shown when missing the `.env` or `.env.defaults` files.

### path (_default: .env_)

The main `.env` file that contains your variables.

- Accepts `string` or `string[]` in code.
- Accepts comma-separated paths via environment variable:
    - `DOTENV_CONFIG_PATH=./.env.base,./.env.dev`
- Merge order is deterministic:
    - load each `path` entry in order
    - later entries override earlier keys

### defaults (_default: .env.defaults_)

The file that default values are loaded from.

- Accepts `string` or `string[]` in code.
- Accepts comma-separated paths via environment variable:
    - `DOTENV_CONFIG_DEFAULTS=./.env.defaults.base,./.env.defaults.shared`
- Merge order is deterministic:
    - load each `defaults` entry in order
    - later entries override earlier keys
    - `path` layers are applied after all `defaults` layers, so `path` still overrides `defaults`

### schema (_default: .env.schema_)

The file that contains the schema of what values should be available from combining `.env` and `.env.defaults`

### schemaExtends (_default: undefined_)

Optional schema extension file(s) layered on top of `schema`.

- Accepts `string` or `string[]` in code.
- Accepts comma-separated paths via environment variable:
    - `DOTENV_CONFIG_SCHEMA_EXTENDS=./.env.production.schema,./.env.region.schema`
- Merge order is deterministic:
    - load base `schema` first
    - then apply `schemaExtends` in order
    - later layers override earlier keys

### errorOnMissing (_default: false_)

Causes the library to throw a `MISSING CONFIG VALUES` error listing all of the variables missing the combined `.env` and `.env.defaults` files.

### errorOnExtra (_default: false_)

Causes the library to throw a `EXTRA CONFIG VALUES` error listing all of the extra variables from the combined `.env` and `.env.defaults` files.

### errorOnRegex (_default: false_)

Causes the library to throw a `REGEX MISMATCH` error listing all of the invalid variables from the combined `.env` and `.env.defaults` files. Also a `SyntaxError` is thrown in case `.env.schema` contains a syntactically invalid regex.

### errorOnMissingFiles (_default: false_)

Causes the library to throw a `MISSING CONFIG FILE` error when configured dotenv files cannot be found. This applies to `path`, `defaults`, and `schema` when they are loaded.

### includeProcessEnv (_default: false_)

Causes the library add process.env variables to error checking. The variables in process.env overrides the variables in .env and .env.defaults while checking

### returnSchemaOnly (_default: false_)

Causes the returned object to include only variables present in `.env.schema`. This is useful when using `includeProcessEnv` for validation but you only want schema-defined keys in the final result.

### assignToProcessEnv (_default: true_)

Sets whether the loaded values are assigned to the `process.env` object. If this is `false`, values are only available in the returned object from `.load()`.

### overrideProcessEnv (_default: false_)

By defaut, `dotenv-entended` will not overwrite any varibles that are already set in the `process.env` object. If you would like to enable overwriting any already existing values, set this value to `true`.

### Layered File Precedence

When using multiple files, merge precedence is:

1. `defaults` layers in order (last wins)
2. `path` layers in order (last wins)
3. `process.env` values, if `includeProcessEnv` is true and `overrideProcessEnv` is false

Example:

```javascript
const config = require('dotenv-extended').load({
    defaults: ['./env/.env.defaults.base', './env/.env.defaults.region'],
    path: ['./env/.env.base', './env/.env.production'],
});
```

Equivalent via environment variables:

```bash
DOTENV_CONFIG_DEFAULTS=./env/.env.defaults.base,./env/.env.defaults.region \
DOTENV_CONFIG_PATH=./env/.env.base,./env/.env.production \
node app.js
```

## Examples

Consider the following three files:

```
# .env file
DB_HOST=localhost
DB_USER=databaseuser-local
DB_PASS=databasepw!
SHARE_URL=http://www.example.com
```

```
# .env.defaults
DB_USER=databaseuser
DB_DATABASE=MyAppDB
```

```
# .env.schema
DB_HOST=[a-z]+
DB_USER=[a-z]+
DB_PASS=
DB_DATABASE=
API_KEY=
```

### Load files with default options

```javascript
const myConfig = require('dotenv-extended').load();

(myConfig.DB_HOST === process.env.DB_HOST) === 'localhost';
(myConfig.DB_USER === process.env.DB_USER) === 'databaseuser-local';
(myConfig.DB_PASS === process.env.DB_PASS) === 'localhost';
(myConfig.DB_DATABASE === process.env.DB_DATABASE) === 'MyAppDB';
(myConfig.SHARE_URL === process.env.SHARE_URL) === 'http://www.example.com';
```

### Load files with `errorOnMissing`

```javascript
const myConfig = require('dotenv-extended').load({
    errorOnMissing: true,
});

// Throws ERROR `MISSING CONFIG VALUES: API_KEY`
```

### Load files with `errorOnExtra`

```javascript
const myConfig = require('dotenv-extended').load({
    errorOnExtra: true,
});

// Throws ERROR `EXTRA CONFIG VALUES: SHARE_URL`
```

### Load files with `errorOnRegex`

```javascript
const myConfig = require('dotenv-extended').load({
    errorOnRegex: true,
});

// Throws ERROR `REGEX MISMATCH: DB_USER`
```

## Contributing

See [CONTRIBUTING.md](CONTRIBUTING.md)

## Migration Notes

### Migrating from legacy 2.x tooling

- Node `>=20` is now required.
- Build/test tooling no longer uses `gulp`, Babel, `esm`, or Mocha/NYC.
- The project now uses:
    - `tsup` for build output in `lib/`
    - `vitest` for tests
    - modern `eslint` config and `prettier`
- Public API is kept compatible (`load`, `config`, `parse`, CLI behavior, and `dotenv-extended/config` preload entry).

## Change Log

See [CHANGELOG.md](CHANGELOG.md)

## License

See [LICENSE](LICENSE)

[dotenv]: https://www.npmjs.com/package/dotenv

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