javascript - AJAX preloader/throbber getting

Question

Below is an AJAX function I'm trying to use to show a loader gif during the request and hide when successful. Basically I started out with the function inside of the response.success which used to work by itself. It creates short urls and sets it to the value of an input field. And I was shown the rest that wraps that function, but i'm getting a 404 error in the console for failure to load resource. I'm sure this is a straightforward answer, I'm too new to tell but I think I'm close. Any help is much appreciated, thanks.

 function getShare(url)
    { 
        $('#loader').show(); // show loading...
        $.ajax({
            dataType: "jsonp",
            jsonpCallback:'apiCallback', // this will be send to api as ?callback=apiCallback because this api do not want to work with default $ callback function name
            url: 'http://b1t.co/Site/api/External/MakeUrlWithGet',
            data: {'url':url},
            success: function(response){
                $('#loader').hide(); // hide loading...
                //respponse = {success: true, url: "http://sdfsdfs", shortUrl: "http://b1t.co/qz"} 
                if(response.success){

                    {       
                    var s = document.createElement('script');
                    var browserUrl = document.location.href;
                    //alert(browserUrl);
                    if (browserUrl.indexOf("?") != -1){
                            browserUrl = browserUrl.split("?");
                            browserUrl = browserUrl[0];
                    }
                    //alert(browserUrl);

                    var gifUrl = $('#gif_input').value;
                    var vidUrl = $('#vid_input').value;
                    //alert(gifUrl + "|" + vidUrl);

                    url = encodeURIComponent(browserUrl + "?gifVid=" + gifUrl + "|" + vidUrl);
                    //alert(encodeURIComponent("&"));
                    s.id = 'dynScript';
                    s.type='text/javascript';
                    s.src = "http://b1t.co/Site/api/External/MakeUrlWithGet?callback=resultsCallBack&url=" + url;
                    document.getElementsByTagName('head')[0].appendChild(s);
                    }

    function resultsCallBack(data)
    {
        var obj = jQuery.parseJSON(JSON.stringify(data));
        $("#input-url").val(obj.shortUrl);
        }
        }
    },
        error:function(){
        $('#loader').hide();
        }
        });
    }