The HTMLAnchorElement.rel property reflects the rel attribute. It is a string containing a space-separated list of link types indicating the relationship between the resource represented by the <a> element and the current document.
A string.
const anchors = document.getElementsByTagName("a");
for (const anchor of anchors) {
alert(`Rel: ${anchor.rel}`);
}<area> and <link>, HTMLAreaElement.rel and HTMLLinkElement.rel.HTMLAnchorElement.relList