Question

我们有以下initialDataSet

0: {ID: 1, Province/State: "", Country/Region: "Thailand", Lat: 15, Long: 101, …}
1: {ID: 2, Province/State: "", Country/Region: "Japan", Lat: 36, Long: 138, …}
2: {ID: 3, Province/State: "", Country/Region: "Singapore", Lat: 1.2833, Long: 103.8333, …}
...

在他们每个人里面我们有：

0:
ID: 1
Province/State: ""
Country/Region: "Thailand"
Lat: 15
Long: 101
data: (62) [{…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {

在每个data:内部，我们有：

data: Array(62)
0: {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0}
1: {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0}
2: {date: "1/24/20", Confirmed: 5, Deaths: 0, Recovered: 0}

我们需要获取total sum of Deaths

我们做到了：

const initialDataSet = [
{ID: 1, "Province/State": "", "Country/Region": "Thailand", Lat: 15, Long: 101, data : [  {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: 0, Recovered: 0}
]},
 {ID: 2, "Province/State": "", "Country/Region": "Japan", Lat: 36, Long: 138, data : [ {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: 0, Recovered: 0}
]},
 {ID: 3, "Province/State": "", "Country/Region": "Singapore", Lat: 1.2833, Long: 103.8333, data: [ {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: 0, Recovered: 0}
]}
];


var testTotals = [];
for (var d = 0; d < initialDataSet.length; d++) {
  var trackObj = initialDataSet[d];
  for (var c = 0; c < trackObj.data.length; c++) {
    testTotals.push(parseInt(trackObj.data[c].Deaths));
  }
}
var myTots = testTotals.reduce((a, b) => a + b, 0);
console.log(myTots);

但是控制台会提供NaN

Answer 1

鉴于您正在使用的（大）data set，可以提取以下额外信息：

时间序列是递增的，这意味着data数组的最后一个值是该时间点的总数；这减少了一个内循环
如果data数组的最后一个值是一个空字符串，则前面没有正整数，这意味着您可以使用|| 0来强制该值

我已经调整了您的数据集以突出显示这些发现，并相应地更改了解决方案。

const initialDataSet = [
{ID: 1, "Province/State": "", "Country/Region": "Thailand", Lat: 15, Long: 101, data : [  {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: '', Recovered: 0}
]},
 {ID: 2, "Province/State": "", "Country/Region": "Japan", Lat: 36, Long: 138, data : [ {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 2, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: 3, Recovered: 0}
]},
 {ID: 3, "Province/State": "", "Country/Region": "Singapore", Lat: 1.2833, Long: 103.8333, data: [ {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 0, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: '', Recovered: 0}
]}
];

const x = initialDataSet.reduce((total, {data}) => {
  const lastItem = data[data.length - 1]
  // it's unlikely, but possible that `data` is an empty array
  return lastItem ? total + (lastItem.Deaths || 0) : total
}, 0)
console.log(x);

Answer 2

数据看起来像是增量数据，因此您只需要对最后的数据求和。
您可以使用reduce来做到这一点。

要处理 NaN ，可以使用~~（非双二进制）将值强制转换为整数。

const initialDataSet = [
{ID: 1, "Province/State": "", "Country/Region": "Thailand", Lat: 15, Long: 101, data : [  
 {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: "", Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: 0, Recovered: 0}
]},
 {ID: 2, "Province/State": "", "Country/Region": "Japan", Lat: 36, Long: 138, data : [
 {date: "1/22/20", Confirmed: 2, Deaths: 'none', Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: "0", Recovered: 0},
 {date: "1/24/20", Confirmed: 5,              Recovered: 0}
]},
 {ID: 3, "Province/State": "", "Country/Region": "Singapore", Lat: 1.2833, Long: 103.8333, data: [
 {date: "1/22/20", Confirmed: 2, Deaths: 0, Recovered: 0},
 {date: "1/23/20", Confirmed: 3, Deaths: 1, Recovered: 0},
 {date: "1/24/20", Confirmed: 5, Deaths: "2", Recovered: 0}
]}
];


var deathsTotals = initialDataSet.reduce((t, {data}) => t + ~~data[data.length-1].Deaths, 0);
  
console.log(deathsTotals)

Answer 3

在循环中添加一个简单的测试：

var testTotals = [];
for (var d = 0; d < initialDataSet.length; d++) {
  var trackObj = initialDataSet[d];
  for (var c = 0; c < trackObj.data.length; c++) {
    testTotals.push(parseInt(trackObj.data[c].Deaths || 0));
  }
}
var myTots = testTotals.reduce((a, b) => a + b, 0);
console.log(myTots);

请注意，除非出于其他原因需要将各个值作为数组使用，否则可以在初始迭代中进行所有数学运算。

您可以做的另一件事是将值显式转换为数字，然后仅在不是NaN的情况下添加值：

var testTotals = [];
for (var d = 0; d < initialDataSet.length; d++) {
  var trackObj = initialDataSet[d];
  for (var c = 0; c < trackObj.data.length; c++) {
    let value = +trackObj.data[c].Deaths;
    if (!isNaN(value))
      testTotals.push(value);
  }
}
var myTots = testTotals.reduce((a, b) => a + b, 0);
console.log(myTots);

这还将处理带有Deaths: "N/A"或其他非数字，非空字符串的条目。

Answer 4

您可以使用嵌套方法进行缩减。

const
    initialDataSet = [{ ID: 1, "Province/State": "", "Country/Region": "Thailand", Lat: 15, Long: 101, data: [{ date: "1/22/20", Confirmed: 2, Deaths: '', Recovered: 0 }, { date: "1/23/20", Confirmed: 3, Deaths: 2, Recovered: 0 }, { date: "1/24/20", Confirmed: 5, Deaths: 3, Recovered: 0 }] }, { ID: 2, "Province/State": "", "Country/Region": "Japan", Lat: 36, Long: 138, data: [{ date: "1/22/20", Confirmed: 2, Deaths: 2, Recovered: 0 }, { date: "1/23/20", Confirmed: 3, Deaths: 4, Recovered: 0 }, { date: "1/24/20", Confirmed: 5, Deaths: 5, Recovered: 0 }] }, { ID: 3, "Province/State": "", "Country/Region": "Singapore", Lat: 1.2833, Long: 103.8333, data: [{ date: "1/22/20", Confirmed: 2, Deaths: 1, Recovered: 0 }, { date: "1/23/20", Confirmed: 3, Deaths: 2, Recovered: 0 }, { date: "1/24/20", Confirmed: 5, Deaths: 3, Recovered: 0 }] }]
    total = initialDataSet.reduce((sum, { data }) =>
        data.reduce((s, { Deaths }) => s + (Deaths || 0), sum), 0);

console.log(total);

如何获取数组中正确的数组和？

4 个答案: