JS how to split the object to two diffrent parts ,like this:

we're going to need more info about exactly what you're trying to do and the structure of your file so we can help plan for problems..

in it's simplest form, the code would go like this:

function splitParts()
{
     var docRef = app.activeDocument;
     var item1 = docRef.pathItems[0];
     var item2 = docRef.pathItems[1];
     item1.top = item1.top + 50;
     item2.top = item2.top - 50;
}
splitParts();