Question

I am trying to post data to the action method in the postData section in jqGrid like this, but get an error, any ideas?

     postData: { species: function() 
                                    {
                                        return JSON.stringify($("form"));
                                    },

I can tell you that this format below does work but it is not JSON:

postData: { species: $("form").serialize() },

Answer 1

Probably you should use jQuery.serializeArray instead of jQuery.serialize:

postData: {
    species: function() {
        return JSON.stringify($("form").serializeArray());
    }
}

See also the answer for some more version of data conversion of the data returned from $("form").serializeArray() before calling of JSON.stringify.