function updatePreview(sourceTagName, previewTagName) {

    var sourceTag = document.getElementById(sourceTagName);
    var previewTag = document.getElementById(previewTagName);

    var isTextArea = (sourceTag.nodeName.toLowerCase() == "textarea");
    var newValue = isTextArea ? sourceTag.value : sourceTag.innerHTML;
     
    previewTag.innerHTML = newValue;

}