conf

What is conf?

The 'conf' npm package is a simple yet powerful configuration management tool for Node.js applications. It allows you to easily store and retrieve configuration data, manage defaults, and handle schema validation. The data is stored in a JSON file, making it easy to read and modify.

What are conf's main functionalities?

Store and Retrieve Configuration Data

This feature allows you to store and retrieve configuration data easily. The data is stored in a JSON file, and you can set and get values using simple methods.

const Conf = require('conf');
const config = new Conf();

// Set a value
config.set('unicorn', '🦄');

// Get a value
console.log(config.get('unicorn'));
//=> '🦄'

Manage Default Values

You can define default values for your configuration settings. If a key is not set, the default value will be returned.

const Conf = require('conf');
const config = new Conf({
  defaults: {
    foo: 'bar'
  }
});

console.log(config.get('foo'));
//=> 'bar'

Schema Validation

You can define a schema for your configuration to ensure that the data meets certain criteria. This helps in maintaining data integrity and consistency.

const Conf = require('conf');
const schema = {
  type: 'object',
  properties: {
    foo: {
      type: 'string'
    },
    bar: {
      type: 'number',
      minimum: 0
    }
  }
};
const config = new Conf({ schema });

config.set('foo', 'baz');
config.set('bar', 42);

console.log(config.get('foo'));
//=> 'baz'
console.log(config.get('bar'));
//=> 42

Other packages similar to conf

configstore

Configstore is another package for managing configuration data in Node.js applications. It provides similar functionality to 'conf', such as storing and retrieving data, managing defaults, and handling schema validation. However, 'conf' offers a more modern API and better TypeScript support.

node-persist

Node-persist is a simple, zero-dependency, key-value storage library for Node.js. It provides persistent storage for configuration data, similar to 'conf'. However, 'conf' offers more advanced features like schema validation and default values management.

nconf

Nconf is a hierarchical configuration manager for Node.js. It supports multiple configuration sources such as command-line arguments, environment variables, and JSON files. While 'nconf' is more flexible in terms of configuration sources, 'conf' is simpler and easier to use for most use cases.

README

conf

Simple config handling for your app or module

All you have to care about is what to persist. This module will handle all the dull details like where and how.

It does not support multiple processes writing to the same store.
I initially made this tool to let command-line tools persist some data.

If you need this for Electron, check out electron-store instead.

Install

npm install conf

Usage

import Conf from 'conf';

const config = new Conf({projectName: 'foo'});

config.set('unicorn', '🦄');
console.log(config.get('unicorn'));
//=> '🦄'

// Use dot-notation to access nested properties
config.set('foo.bar', true);
console.log(config.get('foo'));
//=> {bar: true}

config.delete('unicorn');
console.log(config.get('unicorn'));
//=> undefined

Or create a subclass.

API

Changes are written to disk atomically, so if the process crashes during a write, it will not corrupt the existing config.

Conf(options?)

Returns a new instance.

options

Type: object

defaults

Type: object

Default values for the config items.

Note: The values in defaults will overwrite the default key in the schema option.

schema

Type: object

JSON Schema to validate your config data.

This will be the properties object of the JSON schema. That is, define schema as an object where each key is the name of your data's property and each value is a JSON schema used to validate that property.

Example:

import Conf from 'conf';

const schema = {
	foo: {
		type: 'number',
		maximum: 100,
		minimum: 1,
		default: 50
	},
	bar: {
		type: 'string',
		format: 'url'
	}
};

const config = new Conf({
	projectName: 'foo',
	schema
});

console.log(config.get('foo'));
//=> 50

config.set('foo', '1');
// [Error: Config schema violation: `foo` should be number]

Note: The default value will be overwritten by the defaults option if set.

rootSchema

Type: object

Top-level properties for the schema, excluding properties field.

Example:

import Conf from 'conf';

const store = new Conf({
	projectName: 'foo',
	schema: { /* … */ },
	rootSchema: {
		additionalProperties: false
	}
});

ajvOptions

Type: object

Options passed to AJV.

Under the hood, the JSON Schema validator ajv is used to validate your config. We use JSON Schema draft-2020-12 and support all validation keywords and formats.

Note: By default, allErrors and useDefaults are both set to true, but can be overridden.

Example:

import Conf from 'conf';

const store = new Conf({
	projectName: 'foo',
	schema: { /* … */ },
	rootSchema: {
		additionalProperties: false
	},
	ajvOptions: {
		removeAdditional: true
	}
});

migrations

Type: object

Important: I cannot provide support for this feature. It has some known bugs. I have no plans to work on it, but pull requests are welcome.

You can use migrations to perform operations to the store whenever a project version is upgraded.

The migrations object should consist of a key-value pair of 'version': handler. The version can also be a semver range.

Example:

import Conf from 'conf';

const store = new Conf({
	projectName: 'foo',
	projectVersion: …,
	migrations: {
		'0.0.1': store => {
			store.set('debugPhase', true);
		},
		'1.0.0': store => {
			store.delete('debugPhase');
			store.set('phase', '1.0.0');
		},
		'1.0.2': store => {
			store.set('phase', '1.0.2');
		},
		'>=2.0.0': store => {
			store.set('phase', '>=2.0.0');
		}
	}
});

Note: The version the migrations use refers to the project version by default. If you want to change this behavior, specify the projectVersion option.

beforeEachMigration

Type: Function
Default: undefined

The given callback function will be called before each migration step.

The function receives the store as the first argument and a context object as the second argument with the following properties:

• fromVersion - The version the migration step is being migrated from.
• toVersion - The version the migration step is being migrated to.
• finalVersion - The final version after all the migrations are applied.
• versions - All the versions with a migration step.

This can be useful for logging purposes, preparing migration data, etc.

Example:

import Conf from 'conf';

console.log = someLogger.log;

const mainConfig = new Conf({
	projectName: 'foo1',
	beforeEachMigration: (store, context) => {
		console.log(`[main-config] migrate from ${context.fromVersion} → ${context.toVersion}`);
	},
	migrations: {
		'0.4.0': store => {
			store.set('debugPhase', true);
		},
	}
});

const secondConfig = new Conf({
	projectName: 'foo2',
	beforeEachMigration: (store, context) => {
		console.log(`[second-config] migrate from ${context.fromVersion} → ${context.toVersion}`);
	},
	migrations: {
		'1.0.1': store => {
			store.set('debugPhase', true);
		},
	}
});

configName

Type: string
Default: 'config'

Name of the config file (without extension).

Useful if you need multiple config files for your app or module. For example, different config files between two major versions.

projectName

Type: string

Required unless you specify the cwd option.

You can fetch the name field from package.json.

projectVersion

Type: string

Required if you specify the migration option.

You can fetch the version field from package.json.

cwd

Type: string
Default: System default user config directory

You most likely don't need this. Please don't use it unless you really have to. By default, it will pick the optimal location by adhering to system conventions. You are very likely to get this wrong and annoy users.

Overrides projectName.

The only use-case I can think of is having the config located in the app directory or on some external storage.

encryptionKey

Type: string | Uint8Array | TypedArray | DataView
Default: undefined

Note that this is not intended for security purposes, since the encryption key would be easily found inside a plain-text Node.js app.

Its main use is for obscurity. If a user looks through the config directory and finds the config file, since it's just a JSON file, they may be tempted to modify it. By providing an encryption key, the file will be obfuscated, which should hopefully deter any users from doing so.

When specified, the store will be encrypted using the aes-256-cbc encryption algorithm.

fileExtension

Type: string
Default: 'json'

Extension of the config file.

You would usually not need this, but could be useful if you want to interact with a file with a custom file extension that can be associated with your app. These might be simple save/export/preference files that are intended to be shareable or saved outside of the app.

clearInvalidConfig

Type: boolean
Default: false

The config is cleared if reading the config file causes a SyntaxError. This is a good behavior for unimportant data, as the config file is not intended to be hand-edited, so it usually means the config is corrupt and there's nothing the user can do about it anyway. However, if you let the user edit the config file directly, mistakes might happen and it could be more useful to throw an error when the config is invalid instead of clearing.

serialize

Type: Function
Default: value => JSON.stringify(value, null, '\t')

Function to serialize the config object to a UTF-8 string when writing the config file.

You would usually not need this, but it could be useful if you want to use a format other than JSON.

deserialize

Type: Function
Default: JSON.parse

Function to deserialize the config object from a UTF-8 string when reading the config file.

You would usually not need this, but it could be useful if you want to use a format other than JSON.

projectSuffix

Type: string
Default: 'nodejs'

You most likely don't need this. Please don't use it unless you really have to.

Suffix appended to projectName during config file creation to avoid name conflicts with native apps.

You can pass an empty string to remove the suffix.

For example, on macOS, the config file will be stored in the ~/Library/Preferences/foo-nodejs directory, where foo is the projectName.

accessPropertiesByDotNotation

Type: boolean
Default: true

Accessing nested properties by dot notation. For example:

import Conf from 'conf';

const config = new Conf({projectName: 'foo'});

config.set({
	foo: {
		bar: {
			foobar: '🦄'
		}
	}
});

console.log(config.get('foo.bar.foobar'));
//=> '🦄'

Alternatively, you can set this option to false so the whole string would be treated as one key.

import Conf from 'conf';

const config = new Conf({
	projectName: 'foo',
	accessPropertiesByDotNotation: false
});

config.set({
	`foo.bar.foobar`: '🦄'
});

console.log(config.get('foo.bar.foobar'));
//=> '🦄'

watch

type: boolean
Default: false

Watch for any changes in the config file and call the callback for onDidChange or onDidAnyChange if set. This is useful if there are multiple processes changing the same config file.

configFileMode

Type: number
Default: 0o666

The mode that will be used for the config file.

You would usually not need this, but it could be useful if you want to restrict the permissions of the config file. Setting a permission such as 0o600 would result in a config file that can only be accessed by the user running the program.

Note that setting restrictive permissions can cause problems if different users need to read the file. A common problem is a user running your tool with and without sudo and then not being able to access the config the second time.

Instance

You can use dot-notation in a key to access nested properties.

The instance is iterable so you can use it directly in a for…of loop.

.set(key, value)

Set an item.

The value must be JSON serializable. Trying to set the type undefined, function, or symbol will result in a TypeError.

.set(object)

Set multiple items at once.

.get(key, defaultValue?)

Get an item or defaultValue if the item does not exist.

.reset(...keys)

Reset items to their default values, as defined by the defaults or schema option.

Use .clear() to reset all items.

.has(key)

Check if an item exists.

.delete(key)

Delete an item.

.clear()

Delete all items.

This resets known items to their default values, if defined by the defaults or schema option.

.onDidChange(key, callback)

callback: (newValue, oldValue) => {}

Watches the given key, calling callback on any changes.

When a key is first set oldValue will be undefined, and when a key is deleted newValue will be undefined.

Returns a function which you can use to unsubscribe:

const unsubscribe = conf.onDidChange(key, callback);

unsubscribe();

.onDidAnyChange(callback)

callback: (newValue, oldValue) => {}

Watches the whole config object, calling callback on any changes.

oldValue and newValue will be the config object before and after the change, respectively. You must compare oldValue to newValue to find out what changed.

Returns a function which you can use to unsubscribe:

const unsubscribe = conf.onDidAnyChange(callback);

unsubscribe();

.size

Get the item count.

.store

Get all the config as an object or replace the current config with an object:

conf.store = {
	hello: 'world'
};

.path

Get the path to the config file.

FAQ

How is this different from configstore?

I'm also the author of configstore. While it's pretty good, I did make some mistakes early on that are hard to change at this point. This module is the result of everything I learned from making configstore. Mainly where the config is stored. In configstore, the config is stored in ~/.config (which is mainly a Linux convention) on all systems, while conf stores config in the system default user config directory. The ~/.config directory, it turns out, often have an incorrect permission on macOS and Windows, which has caused a lot of grief for users.

Can I use YAML or another serialization format?

The serialize and deserialize options can be used to customize the format of the config file, as long as the representation is compatible with utf8 encoding.

Example using YAML:

import Conf from 'conf';
import yaml from 'js-yaml';

const config = new Conf({
	projectName: 'foo',
	fileExtension: 'yaml',
	serialize: yaml.safeDump,
	deserialize: yaml.safeLoad
});

Related

• electron-store - Simple data persistence for your Electron app or module
• cache-conf - Simple cache config handling for your app or module