Using nothing but a simple data module and D3, you can build a respectable calendar in (almost) less time than it takes to Google "free calendar component".
Fantastic... I can see pulling a feed of appointments and mapping them to this as a great start. Might be cool to see you elaborate on this by adding appointments.
Where can I find the consts file ?
That comes from the JS file in https://jsbin.com/tijudo/edit, which is loaded in the script tag in the HTML of the lesson's main JSBin.