AppHost

Simple, functional configuration manager. Load and merge config from JSON files, environment variables and cli args.

Install

npm install apphost -P

Usage

// config/index.js
const {
  configure,
  setConfigPath,
  addFile,
  addEnv,
  addArgv
} = require("apphost");

module.exports = configure(
  // Optional. configPath defaults to CWD/config/
  setConfigPath('./config'),
  addFile("appsettings.json"),
  addFile(`appsettings.${process.env.NODE_ENV || "development"}.json`, {
    required: false,
  }),
  addEnv({
    // Optional: merge all env vars starting with prefix
    prefix: 'APP_HOST_',
    // OR explicitly map env var to config object paths
    envToConfigMapping: {
      // process.env.DB_PASSWORD will map to
      // { database: { password: '' }}
      DB_PASSWORD: 'database.password'
    }
  }),
  addArgv({
    // Optional: Specify aliases
    argvAliases: [{ argv: 'app', aliases: ['a'] }],
    // Map argv options to config object paths
    argvToConfigMapping: {
      // -a is an alias for --app.
      // Both will map to { app: { name: '' }}
      app: 'app.name'
    },
  })
);

Config files

addFile supports loading and merging JSON files into the config object.

config/appsettings.json

{
  "app": {
    "name": "MyApp",
    "version": "1.0.0",
    "description": "cool app"
  },
  "database": {
    "url": "",
    "user": "",
    "password": ""
  },
  "logging": {
    "level": "errors"
  }
}

config/appsettings.development.json

{
  "logging": {
    "level": "debug"
  }
}

Environment variables

Enviroment variables map to the config object in two ways.

Variables specified in the envToConfigMapping option map as outlined in the mapping.

Variables that match the prefix option, if provided, are lowercased and then _ are replaced with . in order to map to config object paths.

NODE_ENV=development
# Maps to database.user
APP_HOST_DATABASE_USER=admin
# Maps to database.password
DB_PASSWORD=password123

CLI args

Like environment variables, cli args map to config object in two ways. Those in the argvToConfigMapping are mapped according to the mapping. Alternatively, object paths can be passed directly to the script.

Running the application with

# -a is an alias for --app which maps to app.name
node app.js -a "My Awesome App" --database.url "dbUrl"

Results in

// config
{
  "app": {
    "name": "My Awesome App",
    "version": "1.0.0",
    "description": "cool app"
  },
  "database": {
    "url": "dbUrl",
    "user": "admin",
    "password": "password123"
  },
  "logging": {
    "level": "debug"
  }
};