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如何使用reduce()(es6)计算合计?

ecmascript-6 javascript

stone rock · 技术社区 · 6 年前

我有数据 season 和 fielding 数组。 实战化 数组有3个参数 Catches ,请 Runouts ,请 Stumpings .我想计算总数 捕捉 ,请 树桩 ,请 耗尽 .

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
    }
]

我希望最终输出为以下对象:

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

我的尝试:

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;
        }, {});

我的代码不计算所需的输出并给出 NaN .

2 回复 | 直到 6 年前

CertainPerformance 6 年前

迭代条目属于 fielding ,并将该值添加到累加器中的[key]中(默认为 0 如果密钥尚不存在):

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;
  }, {})
);

baao 6 年前

可以使用reduce和loop 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>

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