jQuery Ajax callbacks not executed

$.ajax({
    url: 'http://example.com',
    data: { foo: 'bar' },
    dataType: 'json',
    success: function (data) { 
        console.log(data); 
    },
    error: function(){
        console.log("Error"); 
    },
    complete: function(){
        console.log("Complete");
    }
});