Infinity Scroll with dynamic items

I am not that great with JS but I created some code to pull info from an XML file and build out the <article> tags. It work great on the first (main page) but break on the portfolio-infinity-scroll-2.html. Here is the code (don’t laugh), I just change it i=n in the for statement or scroll page(s),

    

        var xhttp = new XMLHttpRequest();
        xhttp.onreadystatechange = function () {
            if (this.readyState == 4 && this.status == 200) {
                myFunction(this);
            }
        };
        xhttp.open("GET", "xml/photo_albums.xml", true);
        xhttp.send();

        function myFunction(xml) {

            var xmlDoc = xml.responseXML;
            var i;
            var grouping = xmlDoc.getElementsByTagName("grouping");
            for (i = 0; i " + folder +
                    "" + tag1 +
                    "&nbsp&nbsp " + tag2 +
                    "&nbsp&nbsp " + tag3 +
                    "&nbsp&nbsp " + tag4 +
                    "";
                } else {
                    itemlist += "" + folder +
                    "" + tag1 +
                    "&nbsp&nbsp " + tag2 +
                    "&nbsp&nbsp " + tag3 +
                    "&nbsp&nbsp " + tag4 +
                    "";
                }
            }
            document.getElementById("portfolio").innerHTML = itemlist;
        }

    

And my page URL: http://www.medugno.org/photo_albums.html
Again sorry about the horrible code, but I’m not a JS developer any help would be very much appreciated