Introduction to dotenv-flow

Managing environment variables can be a critical aspect of developing reliable Node.js applications.
dotenv-flow is a powerful and flexible tool that helps you manage environment variables across different environments with ease.

Installation

  
    $ npm install dotenv-flow --save
  

Basic Usage

Create a .env file in the root directory of your project:

  
    NODE_ENV=development
    PORT=3000
    DB_HOST=localhost
  

Then, load environment variables in your Node.js application like this:

  
    require('dotenv-flow').config();

    console.log(process.env.NODE_ENV); // 'development'
    console.log(process.env.PORT); // '3000'
    console.log(process.env.DB_HOST); // 'localhost'
  

Advanced Usage

Multiple Environments

With dotenv-flow, you can have different .env files for different environments:

  
    .env            # <- default
    .env.local      # <- local overwrites
    .env.test       # <- test environment
    .env.production # <- production environment
  

When you set the NODE_ENV to test, then dotenv-flow will automatically load variables from .env.test.

  
    process.env.NODE_ENV = 'test';
    require('dotenv-flow').config();

    console.log(process.env.DB_HOST); // specific value from .env.test
  

Environment Variable Precedence

Precedence order for loading environment variables:

• .env.<NODE_ENV>.local
• .env.local
• .env.<NODE_ENV>
• .env

If a variable is defined in multiple files, the last one wins.

Real-World Application Example

Consider the following app.js that connects to a database:

  
    require('dotenv-flow').config();

    const express = require('express');
    const mongoose = require('mongoose');

    const app = express();
    const port = process.env.PORT || 5000;

    mongoose.connect(\`mongodb://\${process.env.DB_HOST}/mydatabase\`, {
      useNewUrlParser: true,
      useUnifiedTopology: true,
    })
    .then(() => {
      console.log('Connected to MongoDB');

      app.listen(port, () => {
        console.log(\`Server running on port \${port}\`);
      });
    })
    .catch(err => {
      console.error('Failed to connect to MongoDB', err);
    });
  

For different environments, like development and production, you just need to define corresponding .env files, and dotenv-flow will handle the rest.

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