HTMLAnchorElement: relList property

The HTMLAnchorElement.relList read-only property reflects the rel attribute. It is a live DOMTokenList containing the set of link types indicating the relationship between the resource represented by the <a> element and the current document.

The property itself is read-only, meaning you can't substitute the DOMTokenList with another one, but its contents can still be changed.

const anchors = document.getElementsByTagName("a");
for (const anchor of anchors) {
  const list = anchor.relList;
  console.log(
    `New anchor node found with ${list.length} link types in relList.`
  );
  list.forEach((relValue) => {
    console.log(relValue);
  });
}