firefox, backup simple storage

if (!ss.storage.yourSaveData)
    ss.storage.yourSaveData = [{testProp: "test"}];

//setup subfolder
customFolder = dirService.get('ProfD', Ci.nsIFile);
customFolder.append("customFolderName");
if (!customFolder.exists()){
    file.mkpath(stylesFolder.path);
};
// set up for the save json
var customFile = getPathForStorage();
if (customFile && customFile.exists()) {  // read from customFile
    json = file.read(dirStart.path);
    ss.storage.yourSaveData = JSON.parse(json);
}else{  // stor to customFile
    writeStorageForAddon();
};

function getPathForStorage() {
    var dir = dirService.get('ProfD', Ci.nsIFile);
    dir.append('customFolderName');
    dir.append('customStorage.json');
    return dir;
};

function writeStorageForAddon() {
    var stream = file.open(getPathForStorage().path, "w");
    try {
        stream.write(JSON.stringify(ss.storage.yourSaveData));
    } catch (err) {
        stream.close();
    }
    stream.close();
};