Application Configuration Library for Node.js and Browser

• About
• Api

About

Load and Combine Configuration from many sources:

• Files
  • JavaScript Module
  • JSON
  • Yaml
  • ENV + .env
  • S3 Storage
• Directory (combine files)
• MongoDB

Additional features:

• Command Line overrides
• Conditions
• Special Folder
• Interpolations

When combining objects from many sources, deep copy is used:

// a
{ sub: { foo: 'foo' }, arr: [ 'foo' ] }
// b
{ sub: { bar: 'bar' }, arr: [ 'bar' ] }

// combined (a + b)
{
    sub: { foo: 'foo', bar: 'bar'},
    arr: ['foo', 'bar']
}

// E.g you want completely to overwrite `arr` property, then prefix the key's name with `!`

// a
{ sub: { foo: 'foo' }, arr: [ 'foo' ] }
// b
{ sub: { bar: 'bar' }, '!arr': [ 'bar' ] }

// combined (a + b)
{
    sub: { foo: 'foo', bar: 'bar'},
    arr: ['bar']
}

Example:

import AppCfg from 'appcfg'

const config = await AppCfg.fetch([
    // from file. (with Special Folder format syntax support)
    {
        path: '%APPDATA%/.appName/config.yml',

        // set this source as writable for configuration persistance
        writable: true
    },
    // ENV + .env
    {
        dotenv: true,
        // per default CWD is checked, can be overriden
        path: './foo/bar/'
    },
    // directory
    {
        path: 'defaults/**.yml'
    },
    // mongodb
    {
        mongo: 'barSettings'
    },
    // from file, but use only nested property
    {
        path: 'package.json',
        getterProperty: 'atma'
    }
]);

Command Line overrides

Command line arguments are parsed and also set to the configuration object.

$ node app --foo.bar barValue --debug

let config = await Config.fetch(someSources);

assert.has(config, {
    foo: {
        bar: 'barValue'
    },
    debug: true
})

Conditions

Yaml conditions example. (same is also for json format)

# conditional root configuration example
'#if debug':
    name: Foo
    host: dev.example.com
'#if test':
    name: Baz
    host: localhost

# conditional property example
port:
    '#if debug': 5000
    '#if test': 5030
    'default': 8080

# conditional array item example
scipts:
    - lib.js
    - '#if debug || test'
        - lib.debug-extension.js

Arguments lookup:

• in configuration object
• in cli overrides
• in process.env
• compare value as string from process.env.ENV

# from cli example
$ node app --debug

# from environment
$ set ENV=DEBUG
$ node app

{
    name: 'Foo',
    host: 'localhost',
    port: 5000,
    scripts: [
        "lib.js",
        "lib.debug-extension.js"
    ]
}

Special Folder

Use special folders for loading/writing configurations, like %APPDATA% or %HOME%. Is system agnostic and is parsed from the environment variables.

Config.fetch({
    path: '%APPDATA%/.myApplication/global.yml',
    writable: true
});

Interpolations

Sometimes to not repeat the configuration it is convenient to use interpolations. It will embed configuration from itself.

# someConfig.yml
name: 'Foo'
A:
    lorem: '#[name]'
B:
    ipsum: '#[A.lorem]'

let config = await Config.fetch({
    path: 'someConfig.yml'
});

assert.has(config, {
    name: 'Foo',
    A: { lorem: 'Foo' },
    B: { ipsum: 'Foo' }
});

API

Config

static

.fetch(Array<Source>) => Config Instance

Start loading the configuration from specified sources, returns new deferrable configuration instance

methods

<Constructor> (Array<Source>)

• .$read(?Mix)

  • Mix:
    • String: File/Directory/Glob path
    • Source: Source object
    • Array<Source>
    • @default - Array taken from constructor
  • @return: self. Is deferrable, so you can attach done callbacks to it.

  Load configuration from sources

• .$write(config:Object [, ?deepExtend:Boolean, ?setterPath:String):Deferred

  Update and save the configuration. Use first matched writable source.

  • deepExtend: complex objects and arrays are merged
  • setterPath: define nested object in current configuration

• .$get(property:String)

  • property: Dot delimited accessor config.$get('foo.bar.quux')

    // is the same as you if you would write null-check expressions yourself:
    var quuxVal = config.foo && config.foo.bar && config.foo.bar.quux;

  • @return: null or value

• .$is(name:String):Boolean

  Check conditional environment variable, e.g.: config.$is('debug')

  Ways to define the variables. (Example defines DEBUG and TEST flags)

  • directly in the configuration

    // foo.yml
    debug: true
    test: true

  • from the command line:

    > node index --debug --test

  • using environment configuration(comma delimited)

    $ set ENV=DEBUG,TEST
    # also
    $ set NODE_ENV=DEBUG,TEST
    $ node index

• .toJSON():Object

  Returns clean json configuration object.

• .done(callback)

  Fire the callback when the configuration is loaded

Source

Common properties for all source types

{
    // Define specific property to extract SUB-JSON from the loaded configuration
    // @default: null
    getterProperty: String

    // Define specific property in the root configuration,
    // where the loaded configuration should be inserted into
    // @default: null
    setterProperty: String

    // Specify if this source can be used for persistence
    // @default: false
    writable: Boolean

    // Fires before source $read function is called
    // (e.g. change this.path property or any other things)
    beforeRead: Function<Source, RootConfig>

    // Fires after source completes reading
    // (e.g. access config object in `Source.config`)
    afterRead: Function<Source, RootConfig>

    // If true, do not log any warning if the source returns 404
    // @default: false
    optional: true

    // If true, then waits until all previous sources are loaded
    // @default: false
    sync: true
}

FileSource

{
    // File path
    path: String
}

DirectorySource

It will be mapped to multiple FileSources

{
    // Directory path with GLOB look-up, e.g. 'configs/**.json'
    path: String
}

MongoDBSource

Depends on ClassJS

{
    // Collection name
    mongo: String,

    // if source is writable
    // @default: true
    writable: Boolean

    // MongoDB Connection Settings
    // It can be also specified in previous configuration source, under `mongodb` property
    // @default: null -
    settings: {
        // connection string
        connection: String
        // or

        // Port, default 27017
        port: Number,
        // IP, default '127.0.0.1'
        ip: String,

        // Database name, no default
        db: String
    }
}

CustomSource

This source type can suit any needs.

// Constructor with the Deferrable Interface and the method `read`
Function

class Foo {
    config: any
    async read (){
        // do any reads and calcs, after that resolve the source
        this.config = await loadConfig();
    }
}

Embedded

Include config direct into the source

{
    config: Object
}

Test

$ npm install
$ npm test

(c) 2014-2022 MIT License