var xmltext = '<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><root>Hello World</root></rss>';
    var contentType = 'text/xml';
    var file_name = 'rss_feed.xml';

    var pom = document.createElement('a');
    var bb = new Blob([xmltext], {type: contentType});

    pom.setAttribute('href', window.URL.createObjectURL(bb));
    pom.setAttribute('download', file_name);

    pom.dataset.downloadurl = [contentType, pom.download, pom.href].join(':');
    pom.draggable = true;
    pom.classList.add('dragout');

    document.body.appendChild(pom);
    pom.click();
    window.open(pom.getAttribute('href'));
    setTimeout(function(){
        document.body.removeChild(pom);
    },1000);

window.open('data:text/xml;charset=utf-8,' + xmltext, "", "_blank");

window.open('data:application/xml;' + encodeURIComponent(xmltext));

var parser = new DOMParser();
    var xmlDoc = parser.parseFromString(xmltext, "application/xml");

    var oSerializer = new XMLSerializer();
    var sXML = oSerializer.serializeToString(xmlDoc);

    var myXmlWindow = window.open("","");
    myXmlWindow.document.write(sXML);
    myXmlWindow.focus();