Quick observer for reacting to screen orientation in Observable and Quarto notebooks. Assumes portrait on desktop.

islandscape.js

isLandscape = Generators.observe(next => {
  // yield initial value
  next(screen.orientation?.angle == 90 || screen.orientation?.angle == 180);

  // define event listener
  const listener = () => next(screen.orientation?.angle == 90 || screen.orientation?.angle == 180);

  // attach event listener
  screen.orientation.addEventListener("change", listener);

  // return func to cleanup event listener on destruction
  return () => screen.orientation.removeEventListener("change", listener);
})