Using jquery, the following looks exactly like the submitted form to the server side:

    $.ajax({
           type: "POST",
           url: url,
           data: $("#form").serialize(), // serializes the form's elements.
           success: function(data)
           {
               //do stuff
           }
    });

Instead of serializing the form, jquery can also just serialize a flat js object. I wouldn't call that complicated enough to make a distinction. (it's probably really easy in modern plain js too)