Javascript, draw animated path point after point

Question

I have seen people drawing the animated path like this, but if I have an unknown number of points stored in an array, how could I use this callback progressively?

    window.onload = function() {
        var c= Raphael("canvas", 200, 200);
        var p = c.path("M140 100");
        var r = c.path("M190 60");


   p.animate({path:"M140 100 L190 60"}, 2000, function() {
            r.animate({path:"M190 60 L 210 90"}, 2000);
        });
    };