DEV Community

John Au-Yeung
John Au-Yeung

Posted on • Originally published at thewebdev.info

Node.js Basics — App Configuration

Check out my books on Amazon at https://www.amazon.com/John-Au-Yeung/e/B08FT5NT62

Subscribe to my email list now at http://jauyeung.net/subscribe/

Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

Configuration

We can configure our Node app in various ways. We can use it to make our app more flexible.

JSON Files

One way to configure our Node.js app is to read the configuration from one or more JSON files.

For example, we can configure our HTTP server from a JSON file by writing:

config.json

{
  "host": "0.0.0.0",
  "port": 8000
}
Enter fullscreen mode Exit fullscreen mode

index.js

const { port, host } = require('./config.json'),
  http = require('http');

http
  .createServer(function(request, response) {
  })
  .listen(port, host, function() {
    console.log('Listening on port', port, 'and host', host);
  });
Enter fullscreen mode Exit fullscreen mode

We read the configuration from the config.json file.

It’ll automatically be parsed into an object when we call require with the path.

Then we can call createServer and listen methods with it.

We can store multiple configurations with it.

For example, we can write:

config.json

{
  "server": {
    "host": "0.0.0.0",
    "port": 8000
  },
  "database": {
    "host": "db1.example.com",
    "port": 27017
  }
}
Enter fullscreen mode Exit fullscreen mode

index.js

const { server: { port, host } } = require('./config.json'),
  http = require('http');

http
  .createServer(function(request, response) {
  })
  .listen(port, host, function() {
    console.log('Listening on port', port, 'and host', host);
  });
Enter fullscreen mode Exit fullscreen mode

We have a server and database property so that we can store the config for the HTTP server and the config.

Then we destructured the property we need for the HTTP server.

Environmental Variables

We can store our config as environment variables. This way, we can store the settings in our server’s OS or in a file and read them from there.

To do that, we can use the dotenv library.

We can install it by running:

npm i dotenv
Enter fullscreen mode Exit fullscreen mode

Then we can use it by creating and .env file:

HOST=0.0.0.0
PORT=8000
Enter fullscreen mode Exit fullscreen mode

index.js

const http = require('http');
require('dotenv').config()
const { PORT, HOST } = process.env;

http
  .createServer(function(request, response) {
  })
  .listen(PORT, HOST, function() {
    console.log('Listening on port', PORT, 'and host', HOST);
  });
Enter fullscreen mode Exit fullscreen mode

We read the environment variables from the process.env property after we call:

require('dotenv').config()
Enter fullscreen mode Exit fullscreen mode

We store the key-value pairs in the .env file and then read them with the code above into the process.env property.

Arguments

A Node app can also take in arguments.

The command-line arguments will be put into an array and assigned to the process.argv property.

It’ll contain the parts of the command split by spaces.

For example, if we run:

node server.js --port=8001
Enter fullscreen mode Exit fullscreen mode

then process.argv is:

['node', 'server.js', '--port=8001']
Enter fullscreen mode Exit fullscreen mode

We should set some default values if there’s no value set for the command-line argument.

For example, we can write:

const http = require('http');
const [,, PORT = 8080, HOST = '0.0.0.0'] = process.argv;
http
  .createServer(function(request, response) {
  })
  .listen(PORT, HOST, function() {
    console.log('Listening on port', PORT, 'and host', HOST);
  });
Enter fullscreen mode Exit fullscreen mode

We assign the default values as we’re destructuring the command line arguments.

Conclusion

We can configure our Node app in various ways.

Methods include using JSON files, environment variables, and command-line arguments.

Top comments (0)