@lafferty-lounge/config

The lafferty-lounge config package is a simple configuration management package. It handles reading from a file, reading from stdin, environment variables, and command line arguments. It parses everything as yaml so you can use JSON if that's your style.

Usage

test.js

const Config = require('@lafferty-lounge/config');
const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value'], // list the arguments that you want to parse
  ['other-arg']
]);
config.fetch()
  .then(parsedConfig=>{
    console.log(parsedConfig); // { verbosity: null }
  });

config.yaml

option-flag: bar

CLI

echo '{"option-flag": "foo"}' | node test.js -c -         # {'option-flag': 'foo', ...} read from stdin
echo '{"option-flag": "foo"}' | node test.js --config=-

node test.js -c config.yaml                               # {'option-flag': 'bar', ...} read from file
node test.js --config=config.yaml

node test.js -c '{"option-flag": "inline"}'               # {'option-flag': 'inline', ...} read from argv
node test.js --config='{"option-flag": "inline"}'

Reserved flags

• --config
• -c

Both -c and --config are used to tell config where to load a yaml "file" from. (stdin, inline, file)

Type of input

The config module takes several type of inputs for configuration options.

When you create a config instance you'll pass it a prefix to use for environment variables as well as an array of arguments to look for and parse.

const Config = require('@lafferty-lounge/config');
const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value'], // list the arguments that you want to parse
  ['other-arg']
]);
config.fetch()
  .then(parsedConfig=>{
    console.log(parsedConfig); // { 'option-flag': null }
  });

In the previous test.js file you'll notice 'option-flag,o'. That is the option that the config module will attempt to find in your various configurations.

The option-flag key is what config will search for. The c after the comma is the shorthand flag to look for on the command line.

The second item in the option-flag array is the default value to use if no options are found.

NODE_CONFIG will be prefixed to environment variables when parsing options. I.e. for option-flag we'll look for the environment variable NODE_CONFIG_CLI_ARG.

Command Line Arguments

Command line arguments are will be referenced by the same name (dashes included) that you use in your options array. I.e. we'll look for node test.js --option-flag in the following:

const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value']
]);

Shorthand Command Line Arguments

Shorthand command line arguments are optional and are paired with a long hand flag. I.e. we'll end up with { 'option-flag': 'bar' } when we run node test.js -o bar

test.js

const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value']
]);

Environment Variables

When you create a config instance you will pass it a prefix as the first argument. This prefix will be prepended to your options when searching for environment variables.

I.e. We'll look for NODE_CONFIG_OPTION_FLAG using the folling configuration:

test.js

const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value']
]);

Config Files (--config, -c)

Config will parse config files as yaml so you can pass yaml or JSON. Pass the -c or --config arguments when running your application to tell config that you want to load a file.

available --config options

• -
• /filepath
• {"inline": "json"}

Default Values

You can define default values for config options if none of the available places to search have a value defined for them.

We'll end up with { 'option-flag': 'default-value' } if we don't provide any configuration options to the application.

test.js

const config = new Config('NODE_CONFIG', [
  ['option-flag,o', 'default-value']
]);

Precedence

Values take priority from top to bottom in the following order:

1. command line arguments
2. command line shorthand
3. environment variables
4. config file
5. defaults

Example:

test.js

const Config = require('@lafferty-lounge/config');
const config = new Config('CONFIG', [
  ['test-key']
]);
config.fetch()
  .then(parsedConfig=>{
    console.log(parsedConfig);
  });

export CONFIG_TEST_KEY=foo
node test.js                  # { 'test-key': 'foo' }
node test.js --test-key bar   # { 'test-key': 'bar' } command line argument takes precedence here