FAQ: Learn Node.js - Create an HTTP Server

This community-built FAQ covers the “Create an HTTP Server” exercise from the lesson “Learn Node.js”.

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This exercise can be found in the following Codecademy content:

Learn Node.js

FAQs on the exercise Create an HTTP Server

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1 Like

In the exercise, there is a line of code:

const PORT = process.env.PORT || 4001;

I have learned on my own about the short-circuit evaluation. So I know this line of code means that (1) check if process.env.PORT is truthy; (2) if so, assign process.env.PORT as a value of the variable POST; (3) if falsy, then assign 4001.

What I don’t understand is process.env.PORT. We don’t learn this property of the process object. The Node.js documentation (https://nodejs.org/api/process.html#process_process_env) doesn’t mention it either. Is this a property that is initially empty, but once the server gets started, it takes the value of 4001?

2 Likes

In many environments (e.g. Heroku), and as a convention, you can set the environment variable PORT to tell your web server what port to listen on.

So process.env.PORT || 4001 means: whatever is in the environment variable PORT, or 4001 if there’s nothing there.

so you assign PORT=process.env.PORT || 4001 and that makes your server be able to accept a parameter from the environment what port to listen on.

If you assign 4001 hard-coded to PORT , you’re always listening on port 4001, which might be just for you, or not, depending on your requirements and the requirements of the environment in which you’re running your server.

2 Likes

At what point does the ‘request’ parameter of the request listener function come into play? The ‘response’ param gets referenced three or four times but ‘request’ is seemingly never invoked post-declaration?