Environment Variables
What is an Environment Variable (env)
Environment variables are a list of variables that are extracted from an program/application. They are dynamic and can be easily changed based on the environment where the application is being run in. Removing these variables from the application results in a more dynamic application with an added layer of security that increases the speed of setting up a new environment.
Environment Variables can contain the following types:
- System Variables
- User Variables
- Runtime/Process Variables
According to Adam Wiggins and the idea of The Twelve-Factor App,
Env vars are easy to change between deploys without changing any code; unlike config files, there is little chance of them being checked into the code repo accidentally.
and the following should be included in the envs
- Resource handles to the database, Memcached, and other backing services
- Credentials to external services such as Amazon S3 or Twitter
- Per-deploy values such as the canonical hostname for the deploy
Environment Variables in JavaScript
To take advantage of environment variables in JavaScript or NodeJS I recommend using the dotenv npm library. Dotenv is a lightweight module that assists in loading envs from a .env file into process.env.
First, create a .env file by running sudo nano .env in the root of your project and add any desired variables. The file should look similar to that below:
DB_HOST='192.168.4.2'
DB_USER='db-user'
DB_PASSWORD='db-password'
DB_DATABASE='db-schema'
UI_PORT=2222
Installing dotenv
npm install dotenv
Using dotenv
In order to use dotenv, you need to require the dotenv package in the NodeJS file. To do so, include the following require statement.
require('dotenv').config();
Now if you console.log(process.env); the output should look similar to that below with your .env contents being appended to the object:
{
LANGUAGE: 'en_US.UTF-8',
NO_AT_BRIDGE: '1',
LANG: 'en_US.UTF-8',
LS_COLORS: 'rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.oga=00;36:*.opus=00;36:*.spx=00;36:*.xspf=00;36:',
TERM: 'xterm',
DISPLAY: 'localhost:10.0',
LC_ALL: 'en_US.UTF-8',
PATH: '/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin',
MAIL: '/var/mail/root',
LOGNAME: 'root',
USER: 'root',
HOME: '/root',
SHELL: '/bin/bash',
SUDO_COMMAND: '/usr/bin/node app.js',
SUDO_USER: 'pi',
SUDO_UID: '1000',
SUDO_GID: '1000',
DB_HOST: '192.168.4.2',
DB_USER: 'db-user',
DB_PASSWORD: 'db-password',
DB_DATABASE: 'db-schema',
UI_PORT: '2222'
}
Now the environment variables can be called using the following:
let host = process.env.DB_HOST;