Start by importing the module into your application using require or the newer ES2015 import:

var nhabit = require('nhabit');
import nhabit from 'nhabit';

The function requires a path argument, and optional collection and default arguments.

nhabit(path, [collection, default])

The path argument is used as a prefix filter, and can be specified as an array, dot notation, or snake notation. Matches are always case insensitive. If the path is a partial prefix, the remaining portion of the environment variable is parsed and converted to an Object of nested properties.

export MYAPP_MYDB_SERVER_PORT=8080
export MYAPP_MYDB_SERVER_HOST="www.mydb.com"

In reference to the environment variables specified above, the following path arguments are all equivalent and return the same result:

var server = nhabit(['myapp', 'mydb', 'server']);
var server = nhabit('myapp.mydb.server');
var server = nhabit('myapp_mydb_server');
var server = nhabit('mYapp_myDB_seRVer');

/*
    server = {
      port: 8080,
      host: "www.mydb.com"
    }
*/

If the path matches the full name of a variable, the value is returned.

var port = nhabit('myapp.mydb.server.port') //-> 8080

The collection argument defaults to process.env, but any Object containing environment style keys can be used.

var settings = {
  'MYAPP_MYDB_SERVER_PORT': 8080,
  'MYAPP_MYDB_SERVER_HOST': 'www.mydb.com'
}

var server = nhabit('myapp.mydb.server', settings)

/*
    server = {
      port: 8080,
      host: "www.mydb.com"
    }
*/

The value specified for default is returned if no variable matches the specified path, otherwise it returns undefined.

var server = nhabit('myapp.myq.server.port', {}, 8080) //-> 8080

In the above example, we are providing an empty collection, so the default value is returned. The default value can be a simple type, an Array, or an Object.