How to send date from JQuery datepicker to Node.js server

I want to send data from my JQuery datepicker to my Node.js server. I've got this piece of code:

                    <script>
                        $("#dp1").datepicker({
                            dateFormat: "dd-mm-yy",
                            buttonImage: '/img/calendar.png',
                            buttonImageOnly: true,
                            changeMonth: true,
                            changeYear: true,
                            showOn: 'both',
                        });
                    </script>

And datepicker appears after clicking on image. I don't know how to send the chosen date to my Node.js server after chosing the date by the user.

EDIT: Ok, now I have something like this:

                    <script>
                        $("#dp1").datepicker({
                            buttonImage: '/img/calendar.png',
                            onSelect: function(date) {
                                $.ajax({
                                    type: "POST",
                                    url: "/postDate",
                                    data: { date: date }
                                });
                            }
                            dateFormat: "dd-mm-yy",

                            buttonImageOnly: true,
                            changeMonth: true,
                            changeYear: true,
                            showOn: 'both',
                        });
                    </script>

And now my image is not visible and I can't click on it to show the datepicker.

Couple of things, first you need to have a dataType in ajax call. Over here we can use json which you require to pass. and the second would be to stringify the date

So the sample code which demostrates this is (do check the console in the fiddle provided below):

$(function() {
    $("#datepicker").datepicker({
        onSelect:function(date) {

                                $.ajax({
                                    type: "POST",
                                    url: "/echo/json/",
                                    dataType: 'json',
                                    data: { json: JSON.stringify(date) },
                                    success: function(data){    
                                        console.log(data);                  
            }   
                                });
                            }
    });
});

DEMO