I am having trouble sending JavaScript objects as a http request that only accepts json content-type. i.e "application/json" or "text/json"

But, I am not sure why data2 ( stringified json ) works fine But, data1 ( json object ) does throws 400 ( Bad Request ). i.e I am not sure jQuery does not serialize the json object to a valid json string for the server to process.

var data1 = ({ rating : 3 });  //does not work
var data2 = '{ "rating" : 3}'; //works fine

$.ajax({
    url : "/rate",
    data : data1,
    type : "POST",
    contentType: "application/json",
    success: function(json){
        console.log("Ajax Return :"+json);
    }
});