Add nodes to XML

Question

My script asks different types of input to the user and I want to store that info in a settings xml file. That way the dialogs can fall back on previously entered data.
I found out how to read an XML file and search for specific values (xpath), but I also want to add new "settings" to the file. Is there an easy way to do this with InDesign javascript? The code in bold is pseudocode that I want to replace by some real code.
    var settingsFile = new File(kSettingsFileName);
    if (settingsFile.open("r")) {
        var settingsXML = new XML(settingsFile.read());
        settingsFile.close();
        var currentSettingElement = settingsXML.xpath (settingName);
        if currentSettingElement does not exist
            create the element and set the value
        else
            currentSettingElement.setChildren(settingValue);

Answer 1

I use app.insertLabel() and app.extractLabel() to store and retrieve settings in a dialog box. It is more convenient than using extra txt or xml file.
If you are interested, take a look at this script.
This function creates default settings if they have not been saved yet.
function GetSettings() {
     var mySettings = eval(app.extractLabel("Kas_PackageForArchive_Settings_ver3.0"));
     if (mySettings == undefined) {
          mySettings = { copyFontsCheckBox:false, copyGraphicsCheckBox:true, updateGraphicsCheckBox:true, includeHiddenLayers:true, ignorePreflightErrorsCheckBox:true, createReportCheckBox:false, createLogCheckBox:true };
     return mySettings;
Read saved settings before creating a dialog:
function CreateDialog() {
     var mySettings = GetSettings();
     var myDialog = new Window('dialog', 'Package for Archive');...
Save chosen settings before closing the dialog after OK button was clicked:
...     var myShowDialog = myDialog.show();
     if (myShowDialog== 1) {
          var myResult = {};
          myResult.copyFontsCheckBox = myCopyFontsCheckBox.value;
          myResult.copyGraphicsCheckBox = myCopyGraphicsCheckBox.value;
          myResult.updateGraphicsCheckBox = myUpdateGraphicsCheckBox.value;
          if (myInDesignVersion == 6) myResult.includeHiddenLayers = myIncludeHiddenLayersCheckBox.value;
          myResult.ignorePreflightErrorsCheckBox = myIgnorePreflightErrorsCheckBox.value;
          myResult.createReportCheckBox = myCreateReportCheckBox.value;
          myResult.createLogCheckBox = myCreateLogCheckBox.value;
          myResult.folder = myFolder;
          app.insertLabel("Kas_PackageForArchive_Settings_ver3.0", myResult.toSource());
     return myResult;
Kasyan