javascript - Array.filter 没有返回预期的输出

Question

我有一个嵌套的数据数组。我能够根据我的条件获取第一组数据，但是当我对此结果集应用 Array.filter 时，它没有给我预期的结果。

{
  "data": [
    {
      "Date": "02/04/2019",
      "Total": "1000",
      "Success": "850",
      "Failure": "150",
      "FailureDeatils": [
        {
          "name": "Reason1",
          "Count": 2,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        },
        {
          "name": "Reason2",
          "Count": 6,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        }
      ]
    },
    {
      "Date": "03/04/2019",
      "Total": "800",
      "Success": "750",
      "Failure": "150",
      "FailureDeatils": [
        {
          "name": "Reason1",
          "Count": 3,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        },
        {
          "name": "Reason2",
          "Count": 1,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        }
      ]
    }
  ]
}

首先，我应用了以下Array.filter来根据日期获取FailureDetails:

var filtered = data
          .filter(value => value.Date == "02/04/2019")
          .map(e => e.FailureDeatils);

这将产生以下输出:

FailureDeatils:[{"name":"Reason1","Count":2,"Description":[{"DescriptionID": "01","Status": "Failure Point1"},{"DescriptionID": "01","Status": "Failure Point1"}]},{"name":"Reason2","Count":6,"Description":[{"DescriptionID": "01","Status": "Failure Point1"},{"DescriptionID": "01","Status": "Failure Point1"}]}]

现在根据Reason，即Reason1或Reason 2，我想获取描述。但是当我对其应用 Array.filter 时，它返回的输出为未定义。

我哪里出错了？

Answer 1

您可以在过滤后的数组上应用过滤器来获取结果，但是由于它将是一个数组的数组，因此您需要在过滤之前映射过滤后的数组。

但是，您可以简单地使用化简器来展平初始 FailureDescription 数组，而不是映射它。

var data = [
    {
      "Date": "02/04/2019",
      "Total": "1000",
      "Success": "850",
      "Failure": "150",
      "FailureDeatils": [
        {
          "name": "Reason1",
          "Count": 2,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        },
        {
          "name": "Reason2",
          "Count": 6,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        }
      ]
    },
    {
      "Date": "03/04/2019",
      "Total": "800",
      "Success": "750",
      "Failure": "150",
      "FailureDeatils": [
        {
          "name": "Reason1",
          "Count": 3,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        },
        {
          "name": "Reason2",
          "Count": 1,
          "Description": [
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            },
            {
              "DescriptionID": "01",
              "Status": "Failure Point1"
            }
          ]
        }
      ]
    }
  ]

var filtered = data
          .filter(value => value.Date == "02/04/2019")
          .reduce((acc,e) => acc.concat(e.FailureDeatils), []);
          
const reason = "Reason1";


var res = filtered.filter((data) => data.name == reason).reduce((acc, item) =>{
    acc = acc.concat(item.Description);
    return acc;
}, []);

console.log(res);