[Dart] Visit All Sibling Elements or Nodes

var sibling = elm.nextElementSibling;
while (sibling != null) {
  // do something with the sibling element

  sibling = sibling.nextElementSibling;
}
sibling = elm.previousElementSibling;
while (sibling != null) {
  // do something with the sibling element

  sibling = sibling.previousElementSibling;
}

var sibling = node.nextSibling;
while (sibling != null) {
  // do something with the sibling node

  sibling = sibling.nextSibling;
}
sibling = node.previousSibling;
while (sibling != null) {
  // do something with the sibling node

  sibling = sibling.previousSibling;
}