W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<body>

<p id="demo">Click the button to create, and add, a CDATASection</p>

xhttp.open("GET","books.xml",false);
xhttp.send();
var xmlDoc=xhttp.responseXML;
var price=xmlDoc.getElementsByTagName("price")[0];
var txt="Before adding the CDATASection:<br>";
txt=txt + price.childNodes[0].nodeValue;
var cdat=xmlDoc.createCDATASection(" Now on sale: 9.99");
price.appendChild(cdat);
txt=txt + "<br>After adding the CDATASection:<br>"
txt=txt + price.childNodes[0].nodeValue;
txt=txt + price.childNodes[1].nodeValue;
document.getElementById("demo").innerHTML=txt;
};
</script>

<p>The xml file used in the example: <a target="_blank" href="books.xml">books.xml</a></p>

<p><strong>Note:</strong> The createCDATASection is intended for the XML DOM, and will not work for HTML documents.</p>

</body>
</html>