Assigning arguments to local variables in closure

Here is a currying snippet from javascript patterns:

function add(x, y) {
    var oldx = x, oldy = y;
    if (typeof oldy === "undefined") { // partial
        return function (newy) {
             return oldx + newy;
        }
    }
    // full application
    return x + y;
}

ref: https://github.com/shichuan/javascript-patterns/blob/master/function-patterns/currying.html

What is the point of local vars oldx and oldy?