make a list of blogposts based on a rss feed

blogfeed.js

function buildList(ulId, posts) {
    var lis = posts.map(t => { 
        var li = document.createElement("li");
        var link = document.createElement("a");
        link.href = t.url;
        link.appendChild(document.createTextNode(t.title));
        li.appendChild(link);
        return li;
    });
    var ul = document.getElementById(ulId);
    //clear ul
    while( ul.firstChild ){
        ul.removeChild( ul.firstChild );
    }
    lis.forEach(it=> ul.appendChild(it));
}

fetch("http://www.erbrech.com/blog/feed.xml")
    .then( resp => resp.text() )
    .then( txt => { 
        parser = new DOMParser();
        return parser.parseFromString(txt,"text/xml");
    })
    .then(xml => xml.getElementsByTagName("item"))
    .then(items => [].slice.call(items).map(it=>({ "title": it.children[0].textContent, "url": it.children[3].textContent})))
    .then(posts => buildList("blogfeed", posts));