linq.js groupby with Json

This is my Json Object in simplified form.

 var jsonObject =
    [
        {"City":"Monroe","Country":"USA","Latitude":47.8524,"Longitude":-121.98151},
        {"City":"Austin","Country":"USA","Latitude":30.40137,"Longitude":-97.73542},
        {"City":"Austin","Country":"USA","Latitude":30.32198,"Longitude":-97.70864}
    ]

I want to groupBy using City and get the count of records belonging to a specific city, The code that I've tried so far is

    var query2 = $.Enumerable.From(jsonObject)
.GroupBy(
function(record) {return record.City},

function(record) {
        return {City: record.City}
    },
function(rec) {
        return {City:rec}
    }
).ToArray();

I'm still not able to get what i'm doing wrong here. i'm new to linq.js...any help would be appretiated, or atleast point me at right direction.

//group the records

$.Enumerable.From(heatMapObjects)
                                .GroupBy(
                                    "{ City: $.City }",
                                    null,
                                    function (key, g) {
                                        var result = {
                                            City:key.City                                      
                                        };
                                        var groupResults = [];
                                        g.ForEach(function (item) {
                                            groupResults.push(item);
                                        });

                                    //push into array
                                    groupedRecordsCollection.push(groupResults);
                                },
                                "$.City" // compare selector needed
                            )
                            .ToArray();

This solved my problem.