1.2.0 • Public • Published


Opinionated config library that allows you to have complex config, and behaves according to "Twelve Factor App" rules.

Read Motivation section

So, it suits well for:

  1. Local development
  2. Docker environment
  3. AWS Lambda and alternatives

How does it work?

"confme" loads your config and replaces placeholders with environment variables. For environemnt loading it uses dotenv-defaults, so you can create ".env.defaults" file to set default values of environment variables. If you have placeholders for non set environment variables then "confme" will throw an error.

You can pass a path to a JSON/JSON5 file with LIVR rules as a second argument. In this case, it will use LIVR (with extra rules) to validate the config.

Usage examples

Load config

const confme = require("confme");
const config = confme(__dirname + "/config.json");

Load config with validation

const confme = require("confme");

const config = confme(
  __dirname + "/config.json",
  __dirname + "/config-schema.json"

Example config

Placeholders are optional

  "listenPort": "{{PORT}}",
  "apiPath": "https://{{DOMAIN}}:{{PORT}}/api/v1",
  "staticUrl": "https://{{DOMAIN}}:{{PORT}}/static",
  "mainPage": "https://{{DOMAIN}}:{{PORT}}",
  "mail": {
    "from": "MyApp",
    "transport": "SMTP",
    "auth": {
      "user": "{{SMTP_USER}}",
      "pass": "{{SMTP_PASS}}"

Example LIVR schema

See LIVR for details.

  "listenPort": ["required", "positive_integer"],
  "apiPath": ["required", "url"],
  "staticUrl": ["required", "url"],
  "mainPage": ["required", "url"],
  "mail": ["required", {"nested_object": {
    "from": ["required", "string"],
    "transport": ["required", {"one_of": ["SMTP", "SENDMAIL"] }],
    "auth": {"nested_object": {
      "user": ["required", "string"],
      "pass": ["required", "string"]

You can play with it in livr playground

Full example in examples folder.

Try it with

  • node app.js
  • PORT=80 node app.js
  • PORT='AAA' node app.js


According to Twelve Factor App, your config should be passed in envrironment variables. If you are not familiar with ideas of "Twelve Factor App," you should definitely read it.

Having all config variables in env variables is very flexible. You can run your app with docker and without docker. Moreover, you can reuse the same builds across all environments. For example, you can build an image, test it on QA and then run the same image well-tested imaged on production.

But passing the conf in environment variables is not very convenient. So, there a popular library called dotenv which allows you to store environment variables in ".env" files. But you should not commit them and you should have a sample in repository (like ".env.sample" which will be copied to ".env" on deployments without docker).

You can use dotenv-defaults which allows you to have file ".env.defaults" with default values commited to your repository.

But in real life, if you have rather complex configs and you do not want to define all of the values in ENV, you want to use your config as a template and build final config based on this template. It is very common approach for ansible users. confme allows you to do that.

Moreover, confme allows you to define LIVR schema to validate configurations. It can be helpful if you have complex configs with a lot of options but I prefer to use validation schema even with small configs.

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npm i confme

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  • koorchik