To be fair, the parent to your comment included lots of steps that assumed the user was starting from scratch. If we assume the same for the user making an Express app, the steps are much more complex:

* Install a C++ compiler (XCode or libssl-dev packages)

* Run the NVM install script

* Use NVM to install Node.js

* npm install express-generator -g

* express myapp

* cd myapp; npm install

* Install or update Homebrew

* Install git

* git init

* Install Mongo (or your db of choice)

* Install Mongo packages via npm

* npm start