W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<body>

function myFunction(xml) {
    var x, y, z, i, newNode, newTitle, newText, xmlDoc, txt;
    xmlDoc = xml.responseXML;
    txt = "";
    x = xmlDoc.documentElement;
    
    // Create a book element, title element and a text node
    newNode = xmlDoc.createElement("book");
    newTitle = xmlDoc.createElement("title");
    newText = xmlDoc.createTextNode("A Notebook");

// Add a text node to the title node
    newTitle.appendChild(newText);

// Add the title node to the book node
    newNode.appendChild(newTitle);

y = xmlDoc.getElementsByTagName("book")[0];

// Replace the first book node with the new book node
    x.replaceChild(newNode, y);

z = xmlDoc.getElementsByTagName("title");
    // Output all titles  
    for (i = 0; i < z.length; i++) { 
        txt += z[i].childNodes[0].nodeValue + "<br>";
    }
    document.getElementById("demo").innerHTML = txt; 
}
</script>

</body>
</html>

​x
 
<!DOCTYPE html><html><body>​<p id="demo"></p>​<script>var xhttp = new XMLHttpRequest();xhttp.onreadystatechange = function() {    if (this.readyState == 4 && this.status == 200) {        myFunction(this);    }};xhttp.open("GET", "books.xml", true);xhttp.send();​function myFunction(xml) {    var x, y, z, i, newNode, newTitle, newText, xmlDoc, txt;    xmlDoc = xml.responseXML;    txt = "";    x = xmlDoc.documentElement;        // Create a book element, title element and a text node    newNode = xmlDoc.createElement("book");    newTitle = xmlDoc.createElement("title");    newText = xmlDoc.createTextNode("A Notebook");​    // Add a text node to the title node    newTitle.appendChild(newText);​    // Add the title node to the book node    newNode.appendChild(newTitle);​    y = xmlDoc.getElementsByTagName("book")[0];​    // Replace the first book node with the new book node    x.replaceChild(newNode, y);​    z = xmlDoc.getElementsByTagName("title");    // Output all titles      for (i = 0; i < z.length; i++) {         txt += z[i].childNodes[0].nodeValue + "<br>";    }    document.getElementById("demo").innerHTML = txt; }</script>​