problems using $.map() - or maybe it should be done another way

problems using $.map() - or maybe it should be done another way

I'm building a function that gets a JSON array from a database to set the variable equal to that array. The variable can contain an array of several cities, but a simple example at the desired completion of the function is shown below.  Firebug tells me this JSON passes, but I can't get $.map() to complete the function. It should be simple, but I don't understand $.map() to make it work in ajax. Also, maybe there is another way to do this.

So desired result is:

citiesWithBoroughs=[{"city":"New York, New York, United States"}]

The code is:
    citiesWithBoroughs = function (request, response){
        $.ajax({
            url: "getCitiesWithBoroughs.php",
            data: //it works
            type: "POST",
            dataType: "json",
            success: function (data){
                response($.map( data, function (item){










                                        console.log(item.city);
                                        return {city: item.city};
                                }));
                        }
                  });
    }
    citiesWithBoroughs(function(city){
        $each(city, function(){
            alert(item.city  + "|cWB2");
        });
    });