JavaScript - 如何计算 JSON 中的每个键值？

Question

JavaScript - 如何计算 JSON 中的每个键值？

[
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "line", count: 1},
  {date: "2017-09-28", type: "dot", count: 1},
  {date: "2017-09-26", type: "dot", count: 1}
]

使用此 JSON 格式:

[
  {date: "2017-09-26", count: 1},
  {date: "2017-09-28", count: 3}
]

或

最终:

[
  {date: "2017-09-26", dot_count: 1, line_count: 0},
  {date: "2017-09-28", dot_count: 1, line_count: 2}
]

Answer 1

如果哈希不存在，您可以使用哈希表并创建一个新对象。稍后将计数值添加到组中。

var data = [{ date: "2017-09-28", type: "line", count: 1 }, { date: "2017-09-28", type: "line", count: 1 }, { date: "2017-09-28", type: "dot", count: 1 }, { date: "2017-09-26", type: "dot", count: 1 }],
    hash = Object.create(null),
    result = [];
    
data.forEach(function (o) {
    if (!hash[o.date]) {
        hash[o.date] = { date: o.date,  dot_count: 0, line_count: 0 };
        result.push(hash[o.date]);
    }
    hash[o.date][o.type + '_count'] += o.count;
});

result.sort(function (a, b) { return a.date.localeCompare(b.date); });

console.log(result);

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