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2.0.1 • Public • Published


Run package.json scripts by NODE_ENV.

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Install with npm:

npm install by-node-env

Install with pnpm:

pnpm install by-node-env

Install with Yarn:

yarn add by-node-env


  • Read NODE_ENV from process.env.
  • Read NODE_ENV from .env file.
  • Defaults NODE_ENV to development.
  • Customize process.env for each NODE_ENV.
  • Clearer, concise scripts in package.json.
  • No more Bash scripting in package.json.
  • Works on Linux, macOS, and Windows.
  • Compatible with npm, pnpm, and Yarn.
  • Consistent workflow for any NODE_ENV:
    1. npm install or pnpm install or yarn install.
    2. npm start or pnpm start or yarn start.


When developing a Node.js application in development mode, we often use these different commands: npm run serve, npm run watch, npm run dev, etc. In addition, we also set NODE_ENV=development as an environment variable.

When deploying to production, we often use these different commands: npm start, npm build, npm run prod, etc. NODE_ENV=production is a must-have environment variable in this case.

The package.json might look like this for those situations mentioned above:

    "scripts": {
        "watch": "webpack -d --watch",
        "build": "webpack -p",
        "dev": "nodemon src",
        "prod": "node dist",
        "serve": "npm run watch & npm run dev",
        "start": "npm build && npm run prod"

Working on multiple projects with different commands can be very confusing and forgetting, especially under heavy cognitive load. As a result, we spend a lot of time consulting the README or the scripts field in package.json.



    "scripts": {
        "build": "by-node-env",
        "build:development": "webpack -d --watch",
        "build:production": "webpack -p",
        "start": "by-node-env",
        "start:development": "npm build & nodemon src",
        "start:production": "npm build && node dist"

npm build and npm start have long been the de facto commands to build and start a Node.js application, respectively.

Besides that, NODE_ENV should always be explicitly set as an environment variable for best practice. A lot of popular frameworks expect NODE_ENV to be set as well.

Why not combine both, so that when NODE_ENV=production, executing npm start will spawn npm run start:production. Similarly, when NODE_ENV=development, executing npm start will spawn npm run start:development.

Arbitrary NODE_ENV and scripts work too, refer to more examples below.


The priority order of resolving NODE_ENV is as follows:

  1. Environment variable.
  2. .env file in project root directory.
  3. development (default).

The .env file, if present, must be located in the root directory of your project, where package.json lie.

The resolved NODE_ENV is available as process.env.NODE_ENV in your application at runtime.


Example 1a

Example 1a: package.json

    "scripts": {
        "start": "by-node-env", // 1
        "start:development": "ts-node src", // 2a
        "start:production": "ts-node-dev src" // 2b
  1. npm start: 1 ➡️ 2a
  2. NODE_ENV=development npm start: 1 ➡️ 2a
  3. NODE_ENV=production npm start: 1 ➡️ 2b

Example 1b

Example 1b: .env


Example 1b: package.json

    "scripts": {
        "start": "by-node-env", // 1
        "start:development": "ts-node src", // 2a
        "start:production": "ts-node-dev src" // 2b
  1. npm start: 1 ➡️ 2b
  2. NODE_ENV=development npm start: 1 ➡️ 2a
  3. NODE_ENV=production npm start: 1 ➡️ 2b

Example 2

Example 2: package.json

    "scripts": {
        // If NODE_ENV is missing, defaults to "development".
        "build": "by-node-env",
        "build:development": "webpack -d --watch",
        "build:production": "webpack -p",
        "build:staging": "webpack -p",
        // Deployment will not work unless NODE_ENV=production is explicitly set.
        "deploy": "by-node-env",
        "predeploy:production": "docker build -t ${DOCKER_USER}/${DOCKER_PROJECT} .",
        "deploy:production": "docker push ${DOCKER_USER}/${DOCKER_PROJECT}",
        // "npm start" is _the_ command to start the server across all environments.
        "start": "by-node-env",
        "start:development": "npm run build:development",
        "prestart:production": "npm run build",
        "start:production": "start-cluster build/server/server.js",
        "prestart:staging": "npm run build",
        "start:staging": "start-cluster build/server/server.js",
        // Explicitly set NODE_ENV, which is helpful in CI.
        "test": "NODE_ENV=test by-node-env",
        "test:test": "mocha"


Encounter bugs or having new suggestions?

Issues, comments, and PRs are always welcomed!

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