Also, some precision would be appreciated in the language. Example:
> Inside the method connectedCallback(), we define all the functionality the element will have when the element is connected to the DOM.
This is not what happens. connectedCallback appears to be called AFTER the element HAS connected to the DOM.
Of course, in practice, the constructor also appears to be called after the element has connected. Unclear if this is intentional, but lots of tutorials rely on it.