linq.js群与Json

Question

这是我的Json对象的简化形式。

 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}
    ]

我想使用groupBy使用city并获取属于特定城市的记录的计数，到目前为止我尝试过的代码是

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

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

我还是搞不懂我在这里做错了什么。我对linq.js...any的帮助是新手，或者至少给我指明了正确的方向。

Answer 1

//将记录分组

$.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();

这解决了我的问题。

Answer 2

所以你只想知道城市的数量？试一试：

var query = Enumerable.From(jsonObject)
    .GroupBy(
        "$.City",
        null,
        "{ City: $, Count: $$.Count() }") // $: Key, $$: Group
    .ToArray();