isFocusableNode.js

const focusableSelectors = [
    'a[href]:not([tabindex^="-"]):not([inert])',
    'area[href]:not([tabindex^="-"]):not([inert])',
    'input:not([disabled]):not([inert])',
    'select:not([disabled]):not([inert])',
    'textarea:not([disabled]):not([inert])',
    'button:not([disabled]):not([inert])',
    'iframe:not([tabindex^="-"]):not([inert])',
    'audio:not([tabindex^="-"]):not([inert])',
    'video:not([tabindex^="-"]):not([inert])',
    '[contenteditable]:not([tabindex^="-"]):not([inert])',
    '[tabindex]:not([tabindex^="-"]):not([inert])'
  ].join(',')

function isFocusable(node) {
  if (node.nodeType !== 1) { return false }
  return (
    node.matches(focusableSelectors) && 
    // is visible
    Boolean(
      node.offsetWidth || 
      node.offsetHeight || 
      node.getClientRects().length
    )
  )
}