【问题标题】：Parse JSON object for unique records解析 JSON 对象以获取唯一记录
【发布时间】：2017-06-13 06:50:03
【问题描述】：

我有以下 JSON 对象：

var data =JSON.parse('[{"Title":"Test 1","State":"Colorado"}, 
                       {"Title":"Test 1","State":"Arizona"},
                       {"Title":"Test 2","State":"Utah"},
                       {"Title":"Test 2","State":"Arizona"},
                       {"Title":"Test 3","State":"Arizona"}]');

如何解析这个 data 对象，以便得到以下输出：

resultData = [{"Title":"Test 1", State: ["Colorado", "Arizona"]},
              {"Title":"Test 2", State: ["Utah", "Arizona"]},
              {"Title":"Test 3", State: ["Arizona"]}]

到目前为止，我尝试了以下操作：

var resultData = {},
groupBy = "Title";

for (var i = 0; i < data.length; i++) {
    if (!resultData[data[i][groupBy]])
        resultData[data[groupBy]] = [];
    resultData[data[i][groupBy]].push(data[i]);
};

但它没有帮助并返回一些奇怪的对象，如下所示：

resultData = [{Test 1: [{State: "Colorado"}, {State: "Arizona"}]},
              {Test 2: [{State: "Utah"}, {State: "Arizona"}]},
              {Test 3: [{State: "Arizona"}]}]

谁能帮我实现同样的目标。

【问题讨论】：

我认为这应该是状态数组State: ["Colorado", "Arizona"]
感谢您的注释！问题已更新！

标签： javascript json parsing object

【解决方案1】：

你想要达到的目标是 reduce 的完美案例：

第 1 步 - 像以前一样解析数据

var data =JSON.parse('[{"Title":"Test 1","State":"Colorado"}, 
                       {"Title":"Test 1","State":"Arizona"},
                       {"Title":"Test 2","State":"Utah"},
                       {"Title":"Test 2","State":"Arizona"},
                       {"Title":"Test 3","State":"Arizona"}]');

第 2 步 - 将具有相同标题的状态合并到数组中

var titles = data.reduce(function(acc, item){
    var title = item.Title;
    var state = item.State;

    if (!Object.prototype.hasOwnProperty.call(acc, title)){
        acc[title] = [];
    }

    acc[title].push(state);
    return acc;
}, {});

第 3 步 - 使用组合状态构建最终数组

var resultData = Object.keys(titles).map(function(title){
    return {
        Title: title,
        State: titles[title]
    }
});

var data = JSON.parse('[{"Title":"Test 1","State":"Colorado"}, {"Title":"Test 1","State":"Arizona"},{"Title":"Test 2","State":"Utah"},{"Title":"Test 2","State":"Arizona"},{"Title":"Test 3","State":"Arizona"}]');

var titles = data.reduce(function(acc, item) {
  var title = item.Title;
  var state = item.State;

  if (!Object.prototype.hasOwnProperty.call(acc, title)) {
    acc[title] = [];
  }

  acc[title].push(state);
  return acc;
}, {});

var resultData = Object.keys(titles).map(function(title) {
  return {
    Title: title,
    State: titles[title]
  }
});

console.log(resultData)

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【讨论】：

【解决方案2】：

您可以使用单循环方法，对相同组的哈希表进行闭包。

var data = [{ Title: "Test 1", State: "Colorado" }, { Title: "Test 1", State: "Arizona" }, { Title: "Test 2", State: "Utah" }, { Title: "Test 2", State: "Arizona" }, { Title: "Test 3", State: "Arizona" }],
    key = 'Title',
    grouped = data.reduce(function (group) {
        return function (r, o) {
            if (!group[o[key]]) {
                group[o[key]] = [];
                r.push({ Title: o.Title, State: group[o[key]] });
            }
            group[o[key]].push(o.State);
            return r;
        };
    }(Object.create(null)), []);

console.log(grouped);

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【讨论】：