Javascript Open Link In Same Window

I have a form that I would like to get the values entered on the page
and go to a new page in the same window. I can make the code work to
open a new window, but I need it to open in the same window. Here is what I have:

function pass_info() {

var info = "";

info += document.form2.productWeight.value;
window.open("/page/shippingrates/calculate_shipping_before.asp"
+ "?" + "weight=" + info,");
}

I know that it is the window.open, but I have not figured out what I
need to do to get it in the same window.