Also, you can set the value for the whole session, but do not because it is dangerous, and you'll have to keep track of when the value was set.

import dotenv from 'dotenv'
dotenv.config()

# comment
SNAKE_CASE=value
FORMAT_CONVENTION = avoid using spaces at end and around equals as they are ignored
QUOTES_OPTIONAL="double quotes"
SINGLE_QUOTES='spaces at end are not ignored in quotes '

const envNum = parseFloat(process.env.TEST_NUM)

let flagVar = false // if false is default
if (process.env.FLAG_VAR === 'true') {
    flagVar = true
}

---
title: Environment Variables in Practice
isPublicLesson: true
useMdx: true
privateVideoUrl: https://stream.mux.com/Nz02lhZ3pHf4CHbb2qW01ZJ6FS00eFA19TrPksZ202uGvZA.m3u8
code: https://gitlab.com/fullstackio/books/newline-course-apps/environment-variables-for-web-developers-app/-/tree/main/code/module_01/lesson_01.02/App?ref_type=heads
---

## Command-line variable declaration

> Unix

`NODE_ENV=development node index.js`

> Windows

Be careful about the spacing.

`SET NODE_ENV=development&& node index.js`

Also, you can set the value for the whole session, but do not because it is dangerous, and you'll have to keep track of when the value was set.

`$env:NODE_ENV = 'production'`

## Configuration

> CommonJS (default)

```javascript
require('dotenv').config()
```

> Module syntax

```javascript
import dotenv from 'dotenv'
dotenv.config()
```

## Dotenv file structure

    # comment
    SNAKE_CASE=value
    FORMAT_CONVENTION = avoid using spaces at end and around equals as they are ignored
    QUOTES_OPTIONAL="double quotes"
    SINGLE_QUOTES='spaces at end are not ignored in quotes '

## Parsing environment variables

> Numbers

```javascript
const envNum = parseFloat(process.env.TEST_NUM)
```

> Boolean

1.  Figure out if `true` is default or `false` is default
2.  Setup if/else

```javascript
let flagVar = false // if false is default
if (process.env.FLAG_VAR === 'true') {
    flagVar = true
}
```

## Links

-   [ChatGPT: Env Variables with dotenv](https://chatgpt.com/share/bd99d02e-f43e-4400-83d8-d5cd84860b4e)
-   [dotenv package](https://www.npmjs.com/package/dotenv)
-   [VSCode lint plugin](https://marketplace.visualstudio.com/items?itemName=dotenv.dotenv-vscode)
-   [New env-file spec](https://nodejs.org/en/learn/command-line/how-to-read-environment-variables-from-nodejs)
-   [Beginners Guide to environment variables](https://www.telerik.com/blogs/beginners-guide-environment-variables)
-   [Environment variables in bash](https://subscription.packtpub.com/book/cloud-and-networking/9781788990554/1/ch01lvl1sec08/declaring-variables#:~:text=To%20declare%20a%20variable%2C%20just,the%20equals%20sign%20(%20%3D%20).&text=As%20you%20can%20see%2C%20to,equals%20sign%20and%20the%20value.)
-   [.env file format](https://www.dotenv.org/docs/security/env)
-   [What is .env?](https://www.codementor.io/@parthibakumarmurugesan/what-is-env-how-to-set-up-and-run-a-env-file-in-node-1pnyxw9yxj)

## Citations

-   How to set NODE_ENV cross platform:
    [NODE_ENV in Node.js](https://www.geeksforgeeks.org/what-is-node_env-in-node-js/)
-   `.env` file format: [dotenv file format](https://hexdocs.pm/dotenvy/dotenv-file-format.html)
-   [Issue while using dotenv with ES6 modules](https://github.com/motdotla/dotenv/issues/133)
-   [Issue: dotenv file is not loading environment variables](https://stackoverflow.com/questions/42335016/dotenv-file-is-not-loading-environment-variables/42335383#42335383)


Kemal Ahmed

Environment Variables in Practice

The purpose of this lesson is to demonstrate how to use environment variables

by setting up a basic node server script.

We're going to be starting off with an empty node script.

To access environment variables, you use the object process.env.

To start, the most important environment variable is node_end, which we access

This is used to hold the name of the configuration set you're currently using.

Most frameworks interface with it in some way.

Let's see what that looks like by console logging in.

To do that, first we're going to add a start script, node_index.js, and then

We'll do npm run start, and we'll notice it's undefined.

The way to set it is when you run the script, you have to enter it into the

In this case, we can use node_end equals something like development, and when

The first exercise we're going to do is to use node_end for a cores check, like

To those who don't know what a cores check is, it's a commonly used security

that can make it difficult to do local testing if left on.

It's not that important to the cores, so if you'd like to learn more, I'll

leave a link in the description below about how it works.

If we want to serve to all domains for some values of node_end and only to one

we can use a blurb like this where we exclusively serve to localhost when node_

Just to make sure this is working, let's show what happens when we print that.

So in the npm run start, we have our value being development, and when we set

But what happens when we want to set which domain that we're going to be

We have to use an environment variable to set the value here, instead of local

We can set it to another environment variable.

In this case, I'm going to call it process.env.server_url.

But how can we set so many variables on the command line? It gets really long.

I mean, yes, we can use the an_end character server_url, but this gets very

Instead, we're going to get our configuration from a file, and that file is

Notice that there's no extensions, there's nothing before the .env.

That is the extension, it's a plain text file.

And we can use this file to set the server_url value, server_url, equals, so

let's keep it at localhost for now, and we'll change it in a little bit.

In fact, to be more realistic, we'll make it a proper URL, port 3000.

Unfortunately, Node can access this file out of the box. We have to use an npm

The way to use it is to require .env, and then we use the configuration

And so when we run that function, npm run_start, notice it says exclusively

Before we continue, let's look at how .env files are structured.

They're pretty flexible, but I like to use them like this because they're

Every variable in .env variables are constants.

So the convention is to use uppercase with underscore, snake-cased, but it is

case sensitive if you do want to change that up.

The values can contain spaces after the equal signs, but I really discourage it

And the values are always strings. They're always strings all the time.

There is a link plugin if you're wondering, and I've linked it in the

description, as well as a few other rules that I advise you follow for how to

So wait, if everything in environment variables is a string, what if we have

numbers or Boolean that we're trying to bring into our project?

Well, for numbers, well, you're going to have to set it to an interim variable

and parse it, but for Boolean values, it's a little bit harder.

To demonstrate, I'm going to add another variable. We'll call it use cores.

So again, yeah, we're doing the use cores example.

And by default, we don't want to use it. We'll say equals false.

And we'll say if process dot n dot use cores equals, well, in this case, we

have to choose between true, like the string true and false, because the

default value of an environment variable is actually undefined.

So if no value is set, it's actually going to be undefined. And we have to use

that thinking to determine which value we're going to check for.

The thing is that we don't want to check for the default value because it could

So in this case, we'll check for true. So if the value is not set, or if it is

false, then it will do the default action, which is served to all actions, the

And otherwise, only specifically if use course is set to true, will it

So what happens if we want to put our dot n file in a custom folder, like a

We'll put create a config folder, and we'll move the dot n file into the config

Now what we have to do is use the path library so that way we can access this.

And then, instead of having config empty, what we can do is we can specify the

path in which the dot n file is loaded from.

In this case, it's in the config folder and it's called dot and B.

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