How to get "fields" like last mod date? Setting "field" in options does nothing.

[pronode]

So I set options like this:

const sitemap = new Sitemapper({ url: host, field: { loc: true, lastmod: true, changefreq: true, priority: true } });

and then

sitemap
	.fetch()
	.then(function (data) {
		console.log(data);
	});

But this just displays an array of sites, nothing more.

Am I missing something here?