Both of the CodePen example links on that page are insidiously broken. The demos appear to work, but they don't actually demonstrate the claimed portal functionality at all:
// These two containers are siblings in the DOM
const appContainer = document.getElementById('app-container');
const modalContainer = document.getElementById('app-container');
Note that both variables refer to the same element.
No problem! And on re-reading my comment, I probably shouldn't have used the word "insidiously", it came off a lot more negative than I intended. Thanks for the quick fix.
