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Dynamic configuration files

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Loads configuration files depending on:

  • argv: node app.js --env production
  • env: export NODE_ENV=production; node app.js

Expects a .js file as config so you can add dynamic content.


npm install dynamic-config --save


defaultEnv: string = "develop"

Define which env should be set as default.

log: boolean = false

Enable logging of path/env resolution.

envName: string = "env"

The argument/env variable name we expect.


// config/index.js 
const DynamicConfig = require("dynamic-config");
const dynamicConfig = new DynamicConfig({
    defaultEnv: "develop",
    log: true
module.exports = dynamicConfig.load(__dirname, "config.js");
// config/develop/config.js 
module.exports = {
    whereami: "develop"
// app.js 
const config = require("./config");
node app.js
{ whereami: 'develop' }
// Set environment via args 
node app.js --env prod
{ whereami: 'prod' }
// Set environment via env 
export env=stage; node app.js
{ whereami: 'stage' }



These plugins allow you to override specific config fields by applying them via env, argv or a separate local config file.

const dynamicConfig = new (require("dynamic-config"))();
// extend from env 
// extend from file 
// extend from argv 
module.exports = dynamicConfig.load(__dirname, "config.js");

Hint: The order in which the plugins are applied is important. In the above code snippet, config fields defined via arguments would override their counterparts from an override file, which itself overrides fields from environment variables. This is probably a suitable order for most projects.

node app.js
{ name: 'superApp', port: 9000 }
// Overwrite via argv 
node app.js --port 80
// ... or ... 
node app.js --port=80
{ name: 'superApp', port: 80 }
// Overwrite via env 
export port=90 node app.js
{ name: 'superApp', port: 90 }
// Order matters... 
export port=90; node app.js --port 80
{ name: 'superApp', port: 80 }

Extend via file

Create a file named the same as your config, but contains .local in front of the extension, like config.js becomes config.local.js.

In the config extension file you can define any subset of the object, that is defined in the main config and it would overwrite the corresponding value. Both configs are merged via deep-assign.

// config.js 
module.exports = {
    a: 1,
    b: {
        c: "c",
        d: 2
    e: 3
// config.local.js 
module.exports = {
    e: "e",
    b: {
        d: "d"
// result 
    a: 1,
    b: {
        c: "c",
        d: "d"
    e: "e"