Help Regarding $.ajax

Help Regarding $.ajax

Hi, i wanted to know whether i could pass a json variable in the date header of the $.ajax method if so then how. For an example i am posting an implementation:

function getData() {
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "http://someWebService",
data: "{ ID :'123abc }",
dataType: "json",
success: function(res) {
alert(res.d);

}
});

In the above example i have hard coded the data i wanted to know how i could pass a json variable because i have tried by putting a variable there instead of the hard coded values to no avail.

Thanks in advance.