"NetworkError: 404 Not Found" - $.post() with jquery

Here is js code in our Rais 3.2 app responding to change of fields whose ids start with 'order_order_items_attributes':

$(function (){
    $(document).on('change', "[id^='order_order_items_attributes'][id$='_name']", function (){
    $.post(window.location, $('form').serialize(), null, "script");
    return false;
  });
});

The $.post() causes the error:

"NetworkError: 404 Not Found  - http://localhost:3000/po/orders/new?parent_record_id=4&parent_resource=ext_construction_projectx%2Fprojects&project_id=4%22"

Here is the window.location:

If we replace $.post() with $.get(), then the code works fine and fires up the ajax response on the server:

$.get(window.location, $('form').serialize(), null, "script");  #works!

But we have to use $.post() because of the large amount of data being posted to the server. The jquery document shows that $.get() and $.post() have exactly the same format. What we missed here with $.post()? Thanks.