how NODE_ENV variable works

process.env.NODE_ENV is an environment variable used in Node.js and various JavaScript environments to indicate the current execution environment of the application. It is commonly used to differentiate between various stages of the development lifecycle, such as development, testing, and production.

Purpose of process.env.NODE_ENV

1. Environment-Specific Configuration:

   • Allows you to configure your application differently based on whether it’s running in development, testing, or production. For example, you might use a different API endpoint or database configuration depending on the environment.

2. Optimization:

   • Many tools and frameworks use NODE_ENV to enable or disable certain features or optimizations. For example, in React, when NODE_ENV is set to "production", it will enable production optimizations and disable development features.

3. Conditional Code Execution:

   • You can write conditional code that only runs in specific environments. This is useful for logging, debugging, or enabling specific features.

Common Values

• "development": Used during development when debugging and development-specific tools are enabled.
• "production": Used in the production environment where the application is deployed for end-users, often with optimizations and minimized code.
• "test": Used during testing phases, where you might need specific configurations or test-specific data.

Setting process.env.NODE_ENV

• In Node.js Applications: You can set NODE_ENV in your command line or script when starting the application.

  Example:

  NODE_ENV=production node app.js
  

• In Scripts: When running scripts in package.json, you can set NODE_ENV inline.

  Example:

  "scripts": {
    "start": "NODE_ENV=production node app.js",
    "dev": "NODE_ENV=development node app.js"
  }
  

• In CI/CD Pipelines: You can configure NODE_ENV through environment settings in your CI/CD platform.

  Example for GitHub Actions:

  jobs:
    build:
      runs-on: ubuntu-latest
      env:
        NODE_ENV: production
      steps:
        - name: Checkout code
          uses: actions/checkout@v2
        - name: Install dependencies
          run: npm install
        - name: Build
          run: npm run build
  

Using NODE_ENV in Your Code

You can access process.env.NODE_ENV in your Node.js application to conditionally execute code based on the environment:

Example in JavaScript/Node.js:

if (process.env.NODE_ENV === 'production') {
  // Production-specific code
  console.log('Running in production mode');
} else if (process.env.NODE_ENV === 'development') {
  // Development-specific code
  console.log('Running in development mode');
} else if (process.env.NODE_ENV === 'test') {
  // Test-specific code
  console.log('Running in test mode');
}

In Frontend Development

For frontend frameworks like React, NODE_ENV is used to conditionally include or exclude development features:

React Example:

if (process.env.NODE_ENV === 'development') {
  // Code or debugging tools only for development
  console.log('Development mode');
}