dynamic-env-cli

A simple Node.js CLI tool and runtime helper to inject and access environment variables dynamically in frontend JavaScript files, especially useful for static sites served via Nginx.

🚀 Features

• Generates a run.sh script that:
  • Serializes environment variables into a string.
  • Replaces ___ENV-VARIABLES___ placeholder in built .js files.
  • Starts the Nginx server.
• Provides a runtime function to access environment variables using getEnvVariable.
• Supports both development (from .env or system) and production (injected string) environments.

📦 Installation

Install globally:

npm install -g dynamic-env-cli

Or use it locally:

npm install dynamic-env-cli --save

🔧 Usage

1. Adding dynamic-env-cli to your build script

Add the CLI tool to your build script in package.json:

{
  "scripts": {
    "build": "your-build-command && dynamic-env-cli"
  }
}

2. Build your frontend project (e.g., React, Vue, etc.)

npm run build

Ensure your build output is in a dist/ or build/ directory.

3. Run the generated script

./dist/run.sh

or

./build/run.sh

🧠 Accessing Environment Variables in Code

import { getEnvVariable } from 'dynamic-env-cli';

const apiHost = getEnvVariable('API_HOST');
console.log('API Host:', apiHost);

• In development, it returns the value from process.env.
• In production, it parses the injected ___ENV-VARIABLES___ string and retrieves the variable.

📝 Example Workflow

# Build your frontend app
npm run build

./build/run.sh 

🐳 Dockerfile Example

You can use the package inside a Docker container to prepare and serve a frontend app.

FROM node:20 AS builder

WORKDIR /app

COPY . .

RUN npm install 

RUN npm run build

FROM nginx:alpine

WORKDIR /usr/share/nginx/html

# Copy build output from builder stage (adjust to your build output folder)
COPY --from=builder /app/build/ .

CMD ["sh", "-c", "sh run.sh --nginx"]

✅ Build and Run the Docker Image

docker build -t your-app .
docker run -p 80:80 --env-file .env your-app

💡 Ensure your .env file is available at build time or mount it at runtime using --env-file.

⚠️ Error Handling

If the environment variables are not injected in production, the library will log a error and fallback will fail gracefully:

[ERROR] Environment variables are not injected yet.
Please ensure the "run.sh" script has executed successfully.

👤 Author

Artur Aleksanyan