Question

我有一个JSON响应，其中包含用户播放音频文件的时间。对于每个音频会话，我都有：

   {"session": {"checkpoints": [
   {"status": "started", "position": 0, "createdAt": "2020-02- 
   20T16:55:37.795Z"}, 
   {"status": "paused", "position": 195, "createdAt": "2020-02- 
   20T16:58:53.917Z"}, 
   {"status": "stopped", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.230Z"},
   {"status": "closed", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.250Z"}], "totalTime": 195}}

我想映射所有totalTime值并找到最大值。做这个的最好方式是什么？我最初所做的是：

      let maxValue = 0
      let data = JSON.parse(audios).data
      for (let totalTime in data) {
        if (data.hasOwnProperty(totalTime)) {
          let value = data[totalTime]
          if (value > maxValue) {
            maxValue = value
          }
        }
      }

Answer 1

您可以像这样以最大totalTime进行会话

// created 2 sessions, with different totalTime as example
const data = [{
    "session": {
      "checkpoints": [{
          "status": "started",
          "position": 0,
          "createdAt": "2020-02-20T16:55:37.795Z"
        },
        {
          "status": "paused",
          "position": 195,
          "createdAt": "2020-02-20T16:58:53.917Z"
        },
        {
          "status": "stopped",
          "position": 195,
          "createdAt": "2020-02-20T17:01:04.230Z"
        },
        {
          "status": "closed",
          "position": 195,
          "createdAt": "2020-02-20T17:01:04.250Z"
        }
      ],
      "totalTime": 195
    }
  },
  {
    "session": {
      "checkpoints": [{
          "status": "started",
          "position": 0,
          "createdAt": "2020-02-20T16:55:37.795Z"
        },
        {
          "status": "paused",
          "position": 195,
          "createdAt": "2020-02-20T16:58:53.917Z"
        },
        {
          "status": "stopped",
          "position": 195,
          "createdAt": "2020-02-20T17:01:04.230Z"
        },
        {
          "status": "closed",
          "position": 195,
          "createdAt": "2020-02-20T17:01:04.250Z"
        }
      ],
      "totalTime": 193
    }
  }
]

const maxSession = data.sort((a, b) => a.totalTime - b.totalTime)[0]
console.log('maxSession', maxSession)

Answer 2

好吧，我假设您有多个条目，例如您作为示例给出的条目，它们都位于一个数组中。就像这样：

var data = [
{"session": {"checkpoints": [
   {"status": "started", "position": 0, "createdAt": "2020-02- 
   20T16:55:37.795Z"}, 
   {"status": "paused", "position": 195, "createdAt": "2020-02- 
   20T16:58:53.917Z"}, 
   {"status": "stopped", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.230Z"},
   {"status": "closed", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.250Z"}], "totalTime": 195}},
{"session": {"checkpoints": [
   {"status": "started", "position": 0, "createdAt": "2020-02- 
   20T16:55:37.795Z"}, 
   {"status": "paused", "position": 195, "createdAt": "2020-02- 
   20T16:58:53.917Z"}, 
   {"status": "stopped", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.230Z"},
   {"status": "closed", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.250Z"}], "totalTime": 195}},
{"session": {"checkpoints": [
   {"status": "started", "position": 0, "createdAt": "2020-02- 
   20T16:55:37.795Z"}, 
   {"status": "paused", "position": 195, "createdAt": "2020-02- 
   20T16:58:53.917Z"}, 
   {"status": "stopped", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.230Z"},
   {"status": "closed", "position": 195, "createdAt": "2020-02- 
   20T17:01:04.250Z"}], "totalTime": 195}}
]

如果我是对的，这就是您想要做的：

排序数组：

var sorted = data.sort((a, b) => b.session.totalTime - a.session.totalTime);

对于每对对象，您将访问要基于其对数组进行排序的值。注意，在减法中我已经颠倒了b和a。那是因为您想对它进行向下排序，所以更大的价值将首先出现。

采用第一个条目，它将是具有最大totalTime的条目：

var entry = sorted[0];

从条目中提取所需的值：

var maxTotalTime = entry.session.totalTime; console.log(maxTotalTime);

我已经显示了上述步骤，因为您请求了最佳解决方案，但是这里是如何纠正您尝试使用的代码的方法：

  let maxValue = 0
  let data = JSON.parse(audios).data
  for (let entry of data) {
      let value = entry.session.totalTime;
      if (value > maxValue) {
        maxValue = value;
      }
  }

在JavaScript中将JSON转换为数组/映射

2 个答案: