Is it possible to copy all files under a specific relative path?

For example: Copy all files under

‘..preSetting’ + ‘/bb/’

to

Folder.desktop + ‘/aa/’

My path structure is as follows, with “Script” at the same level as preSetting:
D:/OO/Script/myscript.jsx
D:/OO/preSetting/bb/

This one below seems wrong.

//var activeDocPath = String(app.activeDocument.fullName);
var copyToPath = String(Folder.desktop + '/aa/');
var sPath = String("/" + PreSetting + '/bb/');
//alert(sourcePath);
//alert(pShortcut);
var copiedFile = copyFile(sPath, copyToPath);
function copyFile(sourcePath, destinationPath) {
    var fp = Folder(sourcePath)
    //get the files in MyFiles
    var f = fp.getFiles();
    alert(f);
    alert(f.length);
    for (var i = 0; i < f.length; i++) {
        //try {
        if (!f[i].exists) {
            throw new Error('File not found: "' + sourcePath + '".');
        }
        else {
            var dup = File(destinationPath);
            f[i].copy(dup)
            return dup;
        }
    }
}