code.js

var buddy = {};
buddy.firstName=$('input[name="fname"]').val();
buddy.lastName=$('input[name="lname"]').val();
buddy.email=$('input[name="email"]').val();

var data = JSON.stringify(buddy);

$.ajax({
    type: 'POST',
    url: "/path/to/handler",
    data: data,
    contentType: 'application/json',
    dataType: 'json',
    success : function (data) {
      // ...
    }, 
    error: function (jqXHR, textStatus, err) {
      // ...
    }
});

overview.md

Successful input

buddy

{ firstName:"foo", lastName:"bar", email:"[email protected]" };

data

'{ "firstName":"foo", "lastName":"bar", "email":"[email protected]" }';

POST sends

{ "firstName":"foo", "lastName":"bar", "email":"[email protected]" }

Failing input

buddy

{ firstName:"foo", lastName:"bar", email:"[email protected]" };

data

'{ "firstName":"foo", "lastName":"bar", "email":"[email protected]" }';

POST sends

{ "firstName":"foo","lastName":"bar","email":"[email protected]" }

and the error function is called with an err object:

"jQuery152011057530349834899_1305758039649 was not called"