Arrays 如何在Http调用过程中提取特定的键/值？

通过HTTP调用，我得到了一个JSON文件，如下所示：

[
    {
        "totalConfirmed": 555,
        "mainlandChina": 548,
        "otherLocations": 7,
        "deltaConfirmed": 555,
        "totalRecovered": 0,
        "confirmed": {
            "total": 555,
            "china": 548,
            "outsideChina": 7
        },
        "deaths": {
            "total": 17,
            "china": 17,
            "outsideChina": 0
        },
        "reportDate": "2020-01-22"
    },
    {
        "totalConfirmed": 654,
        "mainlandChina": 643,
        "otherLocations": 11,
        "deltaConfirmed": 99,
        "totalRecovered": 0,
        "confirmed": {
            "total": 654,
            "china": 643,
            "outsideChina": 11
        },
        "deaths": {
            "total": 18,
            "china": 18,
            "outsideChina": 0
        },
        "reportDate": "2020-01-23"
    }
]

由此，我想存储totalConfirmed、death和reportDate的值。 所以我的回报应该是这样的

{ 
   totalConfirmed : [555,654], 
   death: [17, 18], 
   dates: ["2020-01-22", "2020-01-23"]
}

以下是我在服务中编写的函数。ts：

但不幸的是，它现在起作用了。我有一个错误：

ERROR TypeError: Cannot read property 'totalConfirmedPerDay' of undefined

输入错误：数据历史记录未初始化

public filteredData(): Observable<History> {
  return this.httpClient.get(this.hostURL).pipe(
    map(res => {
      return {
        totalConfirmedPerDay: res.totalConfirmed,
        totalDeathPerDay: res.deaths.total,
        dates: res.reportDate
      };
    })
  );

输入错误：数据历史记录未初始化

public filteredData(): Observable<History> {
  return this.httpClient.get(this.hostURL).pipe(
    map(res => {
      return {
        totalConfirmedPerDay: res.totalConfirmed,
        totalDeathPerDay: res.deaths.total,
        dates: res.reportDate
      };
    })
  );

制作地图的方法是

map((full:any[]) => {   //I don't want full    
   full.map(res=>{  //I want a "resumed" of full
     const obj={        //transform each element of full
       totalConfirmed:res.totalConfirmed,
       totalDeathPerDay:res.deaths.total,
       dates.res.reportDate
     }
     return obj; 
   )
   return full;
  })

制作地图的方法是

map((full:any[]) => {   //I don't want full    
   full.map(res=>{  //I want a "resumed" of full
     const obj={        //transform each element of full
       totalConfirmed:res.totalConfirmed,
       totalDeathPerDay:res.deaths.total,
       dates.res.reportDate
     }
     return obj; 
   )
   return full;
  })

您可以通过以下方式进行操作：

return this.httpClient.get(this.hostURL)
  .pipe(
    map(arr => {
      return arr.map(sub => {
        return {
          totalConfirmed: sub.totalConfirmed,
          totalDeathPerDay: sub.deaths.total,
          dates: sub.reportDate
        };
      });
    })
  )

现在在订阅块中：

.subscribe(res => {
   let op: History = {
     totalConfirmedPerDay: [],
     totalDeathPerDay: [],
     dates: []
   };
   res.forEach(e => {
     op.totalConfirmedPerDay.push(e.totalConfirmedPerDay);
     op.totalDeathPerDay.push(e.totalDeathPerDay);
     op.dates.push(e.dates);
   });
});

您可以通过以下方式进行操作：

return this.httpClient.get(this.hostURL)
  .pipe(
    map(arr => {
      return arr.map(sub => {
        return {
          totalConfirmed: sub.totalConfirmed,
          totalDeathPerDay: sub.deaths.total,
          dates: sub.reportDate
        };
      });
    })
  )

现在在订阅块中：

.subscribe(res => {
   let op: History = {
     totalConfirmedPerDay: [],
     totalDeathPerDay: [],
     dates: []
   };
   res.forEach(e => {
     op.totalConfirmedPerDay.push(e.totalConfirmedPerDay);
     op.totalDeathPerDay.push(e.totalDeathPerDay);
     op.dates.push(e.dates);
   });
});

---

让dataHistory:History={}让dataHistory:History={}不幸的是，你给出的解决方案不起作用。如果您有时间，请使用此链接检查一次：@xdeepakvu不幸的是，您提供的解决方案不起作用。如果您有时间，请使用以下链接查看一次：@xdeepakv