Configuring an Express application

Express comes with a pretty simple configuration system, which enables you to add certain functionality to your Express application. Although there are predefined configuration options that you can change to manipulate the way it works, you can also add your own key/value configuration options for any other usage. Another robust feature of Express is the ability to configure your application based on the environment it's running on. For instance, you may want to use the Express logger in your development environment and not in production, while compressing your responses body might seem like a good idea when running in a production environment.

To achieve this, you will need to use the process.env property. The process.env is a global variable that allows you to access predefined environment variables, and the most common one is the NODE_ENV environment variable. The NODE_ENV environment variable is often used for environment-specific configurations. To...