app.listen() port number 3000 for local, but needs to be custom for heroku
const varName = something.find(function)does not create a duplicate of the found item, it creates a pointer reference
dot env node used to keep secret key secret:
https://www.npmjs.com/package/dotenv
create .env file, add it to .gitignore
require('dotenv').config()const stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);
where STRIPE_SECRET_KEY is stored in .env
similar to the DATABASE_URL which heroku creates/stores for you
app.listen()port number 3000 for local, but needs to be custom for herokuconst varName = something.find(function)does not create a duplicate of the found item, it creates a pointer reference