Require certain environmental variables

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checkenv - Check Your Environment
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A modern best-practice is to store your application's configuration in environmental variables. This allows you to keep all config data outside of your repository, and store it in a standard, system-agnostic location. Modern build/deploy/development tools make it easier to manage these variables per-host, but they're still often undocumented, and can lead to bugs when missing.
This module lets you define all the environmental variables your application relies on in an env.json file. It then provides a method to check for these variables at application launch, and print a help screen if any are missing.


$ npm i -S checkenv


First, define a JSON file called env.json in your project root (see below). Then, add the following line to the top of your project's entry file:

By default, checkenv will print a pretty error message and call process.exit(1) if any required variables are missing. It will also print an error message if optional variables are missing, but will not exit the process.
Screen Shot
If you would like to handle errors yourself, check takes an optional pretty argument which causes it to throw errors instead of printing an error message. This will only result in an error being thrown on missing required variables.
try {
} catch (e) {
  // Do something with this error


Your JSON file should define the environmental variables as keys, and either a boolean (required) as the value, or a configuration object with any of the options below.


  "NODE_ENV": {
    "description": "This defines the current environment",
    "validators": [{
      "name": "in",
      "options": ["development", "testing", "staging", "production"]
  "PORT": {
    "description": "This is the port the API server will run on",
    "default": 3000
  "NODE_PATH": true,
  "DEBUG": {
    "required": false,
    "description": "If set, enables additional debug messages"



Defines whether or not this variable is required. By default, all variables are required, so you must explicitly set them to optional by setting this to false


Describes the variable and how it should be used. Useful for new developers setting up the project, and is printed in the error output if present.


Defines the default value to use if variable is unset. Implicitly sets required to false.


An array of validators that the variable must pass. See validator.js for details about all validators. Format for each validator is:
  /* ... */
  "validators": [
    "validator name", // Option-less validators can be passed as strings
    { // Validators w/ options must be passed as objects
      "name": "validator name",
      "options": options // Option format varies, see below
  /* ... */

Possible validators (see validator.js for details):
- containsoptions should be a string with what the value should contain - equalsoptions should be a string of the exact value - beforeoptions should be a date - afteroptions should be a date - alpha - alphanumeric - ascii - base64 - boolean - date - decimal - fqdn - floatoptions MAY be an object with min or max properties - hex-color - hexadecimal - ip4 — same as ip with "options": 4 - ip6 — same as ip with "options": 6 - ipoptions MAY be number (4 or 6) - iso8601 - enum — alias for in - inoptions MUST be an array of possible values - intoptions MAY be an object with min or max properties - json - lengthoptions MUST be an object with min, max or both - lowercase - mac-address - numeric - url - uuid3 — same as uuid with "options": 3 - uuid4 — same as uuid with "options": 4 - uuid5 — same as uuid with "options": 5 - uuidoptions MAY be a number (3, 4 or 5) - uppercase - regex — alias for matches - regexp — alias for matches - matchesoptions MUST be either a string representing a regex, or an array in the format ["regex", "modifiers"]

See Also

If you like this module, you may also want to check out:
- dotenv Load missing environmental variables from .env - app-root-path Automatically determine
the root path for the current application
- enforce-node-path Enforce the usage of
the `NODE_PATH` environmental variable

Change Log


- Better handling of syntax errors in env.json (thanks yalcindo!)


- Validation (via validator.js)


- Prints default value in help


- Added support for default values - Added support to change filename via setFilename()


- Bugfix — please do not use versions before 1.0.6


- Passes tests for node 0.10 through 5.1


- Initial release