javascript - How to add parameters to jqgrid using setGridParam? -

this code working properly:

$("#list").jqgrid({ ... postdata: { filters:'{"groupop":"and","rules":[{"field":"category_id","op":"eq","data":"mydata"}]}' }, search: true, ... }); 

i tried add these parameters using setgridparam method:

jquery("#list").setgridparam({     postdata: { filters:'{"groupop":"and","rules":[{"field":"category_id","op":"eq","data":"mydata"}]}' },     search: true, }).trigger('reloadgrid'); 

but doesn't work