在JavaScript中如何将时间戳统计结果对象转换为指定数组格式？

原始数据与现有统计逻辑 #

首先，你已经有了包含creation_timestamp_dt和id的原始数据，以及统计各时间戳条目数量的代码：

var data = [
  { creation_timestamp_dt: "2018-04-06T12:08:40Z", id: "110c983b-acd7-48a8-ba35-e4d0b17dfa3d" },
  { creation_timestamp_dt: "2018-04-06T12:08:40Z", id: "c144e409-c81c-470f-a130-fb00018c32a5" },
  { creation_timestamp_dt: "2018-04-12T20:49:35Z", id: "8a9efac8-1529-4355-a66c-0728a93c5341" },
  { creation_timestamp_dt: "2018-04-12T20:49:35Z", id: "949317c5-200c-44fa-84bc-4630fc93ab71" },
  { creation_timestamp_dt: "2018-04-13T16:17:43Z", id: "6c40778e-9033-4afa-83ee-ecbbf1387069" },
  { creation_timestamp_dt: "2018-04-13T16:17:43Z", id: "24d8ad2a-d1f2-4abe-9ec3-03be46eb76bf" },
  { creation_timestamp_dt: "2018-04-14T15:57:40Z", id: "f9b9fa3e-d62f-49f5-a318-917b889c2320" },
  { creation_timestamp_dt: "2018-04-14T15:57:40Z", id: "382ab411-b1c8-4f33-ac9f-b1b123d0fa23" },
  { creation_timestamp_dt: "2018-04-27T16:28:58Z", id: "057e37db-edc9-48ca-83a0-0bafc8d93d6b" },
  { creation_timestamp_dt: "2018-04-27T16:28:58Z", id: "ac5de29b-2552-428e-ab1c-4991597a50ae" },
  { creation_timestamp_dt: "2018-05-02T12:08:23Z", id: "bbb18e83-0197-4e5e-be2f-fc3eb89f7242" },
  { creation_timestamp_dt: "2018-05-02T12:08:23Z", id: "123a1917-ad19-45a9-8d2e-4187e6bf5b6d" },
  { creation_timestamp_dt: "2018-05-10T17:10:46Z", id: "5cb5c197-88df-4247-b5ee-f5e00f3e89a2" },
  { creation_timestamp_dt: "2018-05-10T17:10:46Z", id: "aa70ba56-8128-410d-b5cf-4ad32abc3d8a" },
  { creation_timestamp_dt: "2018-05-10T17:10:46Z", id: "613d8a61-d889-4642-a7de-a9390e97c4b3" },
  { creation_timestamp_dt: "2018-05-15T15:54:43Z", id: "bfbf2a09-6baa-4f72-b1d8-87fc5256093c" },
  { creation_timestamp_dt: "2018-05-15T15:54:43Z", id: "5cd53add-68ed-41c5-b3ee-e844c6d940ea" },
  { creation_timestamp_dt: "2018-05-16T10:41:17Z", id: "7f363766-77b3-4a7b-a539-b30d280e98ac" },
  { creation_timestamp_dt: "2018-05-16T10:41:17Z", id: "a8c9c754-65c9-48e5-a454-c1e98334b850" },
  { creation_timestamp_dt: "2018-05-16T10:45:18Z", id: "cc37be99-d0fb-42f9-a49a-199962beb988" },
  { creation_timestamp_dt: "2018-05-16T10:45:18Z", id: "a3336588-31dd-4864-9ca7-f651cd7457a4" }
];

var counts = {};
for (var i = 0; i < data.length; i++) {
  counts[data[i].creation_timestamp_dt] = 1 + (counts[data[i].creation_timestamp_dt] || 0);
}

这段代码运行后，counts对象会存储每个时间戳对应的条目数量。

转换为目标数组格式 #

要把counts转换成你需要的{timestamp: "...", posts: N}格式的数组，这里有两种实用方案：

方案一：ES6简洁写法（推荐） #

利用Object.entries()和箭头函数快速转换，代码简洁易懂：

// 转换counts为目标数组
var result = Object.entries(counts).map(([timestamp, posts]) => ({
  timestamp,
  posts
}));

// 输出结果
console.log(result);

代码解释

• Object.entries(counts)：将counts对象转换为二维数组，每个子数组格式为[时间戳, 对应数量]，比如["2018-04-06T12:08:40Z", 2]。
• .map(([timestamp, posts]) => ({ timestamp, posts }))：遍历二维数组，解构出时间戳和数量，用对象字面量简写语法生成目标格式的对象。

方案二：兼容旧环境写法 #

如果你的运行环境不支持ES6语法，用传统循环写法也能实现：

var result = [];
for (var timestamp in counts) {
  // 确保只处理对象自身的属性，避免原型链污染
  if (counts.hasOwnProperty(timestamp)) {
    result.push({
      timestamp: timestamp,
      posts: counts[timestamp]
    });
  }
}
console.log(result);

最终输出结果 #

两种方案都会得到你需要的数组：

[
  {timestamp: "2018-04-06T12:08:40Z",posts:2},
  {timestamp:"2018-04-12T20:49:35Z",posts:2},
  {timestamp:"2018-04-13T16:17:43Z",posts:2},
  {timestamp:"2018-04-14T15:57:40Z",posts:2},
  {timestamp:"2018-04-27T16:28:58Z",posts:2},
  {timestamp:"2018-05-02T12:08:23Z",posts:2},
  {timestamp:"2018-05-10T17:10:46Z",posts:3},
  {timestamp:"2018-05-15T15:54:43Z",posts:2},
  {timestamp:"2018-05-16T10:41:17Z",posts:2},
  {timestamp:"2018-05-16T10:45:18Z",posts:2}
]

内容的提问来源于stack exchange，提问作者Harsh