Package Exports

appyconfig
appyconfig/index.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (appyconfig) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

appyconfig

Read application configuration data from different sources in a unified way.

Install

npm install appyconfig

Configuration

Decide on data sources for your configuration tree.
Create a config.js file that resolves and exports your configuration.
Create a configuration tree that reflects your configuration options and specifies how to get the data from each configuration source.
Require your config.js wherever the config is needed.

Data Sources

Examples of data sources are:

Hard coded default values
Environment variables
Command line arguments
JSON configuration file

Each of these data sources has a corresponding Loader class, and most have a key that will represent options in the configuration tree.

Data source	Class	Key	Other considerations
Default values	DefaultValueLoader	default	Key is value to set
Environment variables	EnvLoader	env	Key is the environment variable to fetch
Command line arguments	CmdArgsLoader	cmdArg	Key is the command line option to retrieve
JSON file	JsonLoader	N/A	Specify filename when instantiating JsonLoader

Example

In your lib/config.js:

// Require appyconfig.
const { resolveConfig } = require('appyconfig');

// Define default values and the environment variables that will override them.
const config_tree = {
  "authorize": {
    "client": {
      "id": {
        default: "1234567890",
        env: "APP_CLIENT_ID",
      },
      "secret": {
        default: "password123",
        env: "APP_CLIENT_SECRET",
      }
    },
    "auth": {
      "tokenHost": {
        default: "default",
        env: "APP_AUTH_TOKENHOST",
      }
    }
  },
  "app": {
    "hostname": {
      default: "localhost",
      env: "APP_HOSTNAME",
    },
    "authorizeCallback": {
      default: "https://example.com/authorize",
      env: "APP_AUTHORIZE_CALLBACK_URL"
    },
    "tokenCallback": {
      default: "https://example.com/token",
      env: "APP_TOKEN_CALLBACK_URL"
    },
    "oauthScope": {
      default: "read",
      env: "APP_OAUTH_SCOPE"
    }
  }
}

const config = resolve_config(config_tree);

// Export your config.
module.exports = config;

Customizing the Configuration Resolution Order

By default when running resolve_config(), appyconfig will use default config values (DefaultValueLoader) first, then override those values with environment variables (EnvLoader). This is equivalent to the following code:

const config = resolve_config(config_tree, [
  new DefaultValueLoader,
  new EnvLoader
]);

You can choose to use different sources. For example, to fill the configuration with null values:

const config = resolve_config(config_tree, [new NullLoader])

Commander

If you are using Commander, appyconfig utilizes the preAction hook to grab global command line options.

This means the Command instance must be passed to resolveCommander() so that the hook can be installed. Command-line options will be extracted when the 'preAction' hook is executed (i.e. before actions are run).

Commander Example

In your lib/config:

const { ConfigResolver, DefaultValueLoader, EnvLoader, CmdArgsLoader } = require('appyconfig');

const config_tree = {
  // Define your config tree here.
  // The key for parsing command line args is cmdArgs, and it contains
  // the command line option key to retrieve from program.opts().
  mysetting: {
    default: "defaultValue",
    env: "MYSETTING",
    cmdArg: "mySetting" // --my-setting
  }
};

const resolver = new ConfigResolver();
const config = resolver.resolve_config(config_tree, [
  new DefaultValueLoader,
  new EnvLoader,
  new CmdArgsLoader
]);

module.exports = { config, resolveCommander: resolver.resolveCommander };

In your app.js:

const { Command } = require('commander');
const { resolveCommander } = require('lib/config');

const program = new Command();
resolveCommander(program);

// Set up your program command line options here...

program.parse(process.argv);

And anywhere else you need the configuration:

const { config } = require('lib/config');

// Use the config.