Question

我有包含season和fielding数组的数据。 fielding数组具有3个参数Catches，Runouts，Stumpings。我想计算总计Catches，Stumpings，Runouts。

var data = [
    {
    season:2015,
    fielding:{Catches:2, Runouts:1, Stumpings:1
    },
    {
    season:2016,
    fielding:{Catches:0, Runouts:1, Stumpings:1
    },
    {
    season:2016,
    fielding:{Catches:0, Runouts:0, Stumpings:0
    },
    {
    season:2017,
    fielding:{Catches:1, Runouts:3, Stumpings:1
    },
    {
    season:2017,
    fielding:{Catches:2, Runouts:1, Stumpings:2
    }
]

我希望最终输出作为对象，如下所示：

Catches -> 2+0+0+1+2 = 5
Runouts -> 1+1+0+3+1 = 6
Stumpings -> 1+1+0+1+2 =5

我尝试过的事情：

let dismissals = data.reduce( (a,{season, fielding})  => {

            if(!a[fielding.Catches]){
                a[fielding.Catches] = {};
            }else if(a[fielding.Runouts]){
                a[fielding.Runouts] = {};
            }else if(a[fielding.Stumpings]){
                a[fielding.Stumpings] = {};
            }else{
                a[fielding.Stumpings] += 1;
                a[fielding.Runouts] += 1;
                a[fielding.Catches] += 1;
            }

            return a;
        }, {});

我的代码未计算所需的输出，而是给出了NaN。

Answer 1

遍历fielding的项，然后将值添加到累加器的[key]中（如果该键尚不存在，则默认为0）：

var data=[{season:2015,fielding:{Catches:2,Runouts:1,Stumpings:1}},{season:2016,fielding:{Catches:0,Runouts:1,Stumpings:1}},{season:2016,fielding:{Catches:0,Runouts:0,Stumpings:0}},{season:2017,fielding:{Catches:1,Runouts:3,Stumpings:1}},{season:2017,fielding:{Catches:2,Runouts:1,Stumpings:2}}];

console.log(
  data.reduce((a, { fielding }) => {
    Object.entries(fielding).forEach(([key, val]) => {
      if (key !== '_id') a[key] = (a[key] || 0) + val;
    });
    return a;
  }, {})
);

Answer 2

您可以使用减少并循环fielding的Object.keys

const res = data.reduce((a, {fielding}) =>
    Object.keys(fielding).forEach(f => a[f] = (a[f] || 0) + fielding[f]) || a
, Object.create(null));

console.log(res);

<script>
var data = [
    {
        season:2015,
        fielding:{Catches:2, Runouts:1, Stumpings:1}
    },
    {
        season:2016,
        fielding:{Catches:0, Runouts:1, Stumpings:1}
    },
    {
        season:2016,
        fielding:{Catches:0, Runouts:0, Stumpings:0}
    },
    {
        season:2017,
        fielding:{Catches:1, Runouts:3, Stumpings:1}
    },
    {
        season:2017,
        fielding:{Catches:2, Runouts:1, Stumpings:2}
    }
];

</script>

如何使用reduce（）（ES6）计算总数？

2 个答案: