Question

我正在尝试根据日期获取失败的详细信息。为此，我正在应用array.filter但它返回空数组。

下面是我的数组：

value:[{
  "Date": "02/04/2019",
  "Total": "1000",
  "Success": "850",
  "Failure": "150",
  "FailureDeatils": [{
      "Reason": "Reason1",
      "Count": 2
    },
    {
      "Reason": "Reason2",
      "Count": 6
    }
  ]
}, {
  "Date": "03/04/2019",
  "Total": "800",
  "Success": "750",
  "Failure": "150",
  "FailureDeatils": [{
    "Reason": "Reason1",
    "Count": 3
  }, {
    "Reason": "Reason2",
    "Count": 1
  }]
}]

如果我输入日期为02/04/2019，则应返回以下内容：

{
  "FailureDeatils": [{
      "Reason": "Reason1",
      "Count": 2
    },
    {
      "Reason": "Reason2",
      "Count": 6
    }
  ]
}

我正在使用以下array.filter方法：

var filtered = value.filter(isPresent);
function isPresent(value) {
  return value == 02/04/2019;
}

这将返回空数组。

有人可以找出我要去哪里的地方吗？

Answer 1

在函数isPresent中，value是数组中的每个对象

您正在将整个对象与一个值进行比较

您需要做的是比较该对象的对象属性

function isPresent(value) {
    return value.Date == "02/04/2019";
}

Answer 2

您需要检查value.Date而不是value，因为value或回调参数将保留object中整个迭代的array：

function isPresent(value) {
  return value.Date && value.Date == "02/04/2019";
}

要从过滤后的FailureDeatils中仅获取object，您可以映射 Array#map() method 过滤的结果：

var filtered = data.filter(isPresent).map(o => { return {"FailureDeatils": o.FailureDeatils}});

注意：

请确保在"02/04/2019"之间包装""，以便可以将其评估为string并进行正确比较，否则将其计算为Number并给出错误的过滤条件结果。
避免为数组使用相同的变量名value两次的回调参数，以提高代码的可读性。

演示：

var data = [{
  "Date": "02/04/2019",
  "Total": "1000",
  "Success": "850",
  "Failure": "150",
  "FailureDeatils": [{
      "Reason": "Reason1",
      "Count": 2
    },
    {
      "Reason": "Reason2",
      "Count": 6
    }
  ]
}, {
  "Date": "03/04/2019",
  "Total": "800",
  "Success": "750",
  "Failure": "150",
  "FailureDeatils": [{
    "Reason": "Reason1",
    "Count": 3
  }, {
    "Reason": "Reason2",
    "Count": 1
  }]
}]



var filtered = data.filter(isPresent).map(e => { return {"FailureDeatils": e.FailureDeatils}});

function isPresent(value) {
  return value.Date && value.Date == "02/04/2019";
}

console.log(filtered);

Answer 3

这是基于您的数组的工作代码。

var value = [{
  "Date": "02/04/2019",
  "Total": "1000",
  "Success": "850",
  "Failure": "150",
  "FailureDeatils": [{
      "Reason": "Reason1",
      "Count": 2
    },
    {
      "Reason": "Reason2",
      "Count": 6
    }
  ]
}, {
  "Date": "03/04/2019",
  "Total": "800",
  "Success": "750",
  "Failure": "150",
  "FailureDeatils": [{
    "Reason": "Reason1",
    "Count": 3
  }, {
    "Reason": "Reason2",
    "Count": 1
  }]
}];

var filtered = value.filter (isPresent).map (obj => obj.FailureDeatils);;
function isPresent (value) {
  return value.Date == "02/04/2019";
}

console.log (filtered);

Answer 4

var filtered = value.filter(function(a){
                   return a.Date === "02/04/2019";
               });

Answer 5

您应该这样做-

const value = [{
  "Date": "02/04/2019",
  "Total": "1000",
  "Success": "850",
  "Failure": "150",
  "FailureDeatils": [{
      "Reason": "Reason1",
      "Count": 2
    },
    {
      "Reason": "Reason2",
      "Count": 6
    }
  ]
}, {
  "Date": "03/04/2019",
  "Total": "800",
  "Success": "750",
  "Failure": "150",
  "FailureDeatils": [{
    "Reason": "Reason1",
    "Count": 3
  }, {
    "Reason": "Reason2",
    "Count": 1
  }]
}]

const filtered = value.filter((x) => x.Date === "02/04/2019");

Answer 6

const value = [{
      "Date": "02/04/2019",
      "Total": "1000",
      "Success": "850",
      "Failure": "150",
      "FailureDeatils": [{
          "Reason": "Reason1",
          "Count": 2
        },
        {
          "Reason": "Reason2",
          "Count": 6
        }
      ]
    }, {
      "Date": "03/04/2019",
      "Total": "800",
      "Success": "750",
      "Failure": "150",
      "FailureDeatils": [{
        "Reason": "Reason1",
        "Count": 3
      }, {
        "Reason": "Reason2",
        "Count": 1
      }]
    }]   

    var filtered = value.filter(isPresent).map(row => {
      return {
        FailureDeatils : row.FailureDeatils
      }
    });
    function isPresent(value) {
      return value.Date === "02/04/2019";
    }

    console.log(filtered)

Answer 7

您可以这样做：

const value = [{"Date": "02/04/2019","Total": "1000","Success": "850","Failure": "150","FailureDeatils":[{"Reason":"Reason1","Count":2}, {"Reason":"Reason2","Count":6}]},{"Date": "03/04/2019","Total": "800","Success": "750","Failure": "150","FailureDeatils": [{"Reason":"Reason1","Count":3},{"Reason":"Reason2","Count":1}]}];
const isPresent = ({Date}) => Date === '02/04/2019';
const filtered = value.filter(isPresent);

console.log(filtered);

Array.filter返回空数组

7 个答案: