在js中聚合数组内的对象

Question

我有一个如下所示的数组：[  {"sku": 123, "val": 10}, {"sku": 124, "val":12}, {"sku": 123, "val": 20}]javascript 中是否有一种快速方法可以对val具有相同 sku 属性的对象求和，因此结果将是：[  {"sku": 123, "val": 30}, {"sku": 124, "val":12}]

Answer 1

您可以使用javascript的reduce函数

const array = [ 

 { "sku": 123, "val": 10 },

 { "sku": 124, "val": 12 },

 { "sku": 123, "val": 20 }

];

const result = [];

array.reduce((res, value) => {

  if (!res[value.sku]) {

    res[value.sku] = { "sku": value.sku, "val": 0 };

    result.push(res[value.sku])

  }

  res[value.sku].val += value.val;

  return res;

}, {});

console.log(result)

Answer 2

您应该按 SKU 对条目进行分组，然后将条目映射到 SKU 和减少的值（总和）。

const data = [ 

 { "sku": 123, "val": 10 },

 { "sku": 124, "val": 12 },

 { "sku": 123, "val": 20 }

];

const groupBy = (arr, key) => arr.reduce((acc, entry) => ({

  ...acc, [entry[key]]: [ ...(acc[entry[key]] || []), entry ]

}), {}); 

const sum = Object.entries(groupBy(data, 'sku'))

  .map(([key, values]) =>

    ({

      'sku': key,

      'val': values.reduce((acc, { val }) => acc + val, 0)

    }))

console.log(sum);

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这是一个更加动态的版本，允许使用具有各种聚合技术的多个减速器。

const groupBy = (arr, key) => arr.reduce((acc, entry) => ({

  ...acc, [entry[key]]: [ ...(acc[entry[key]] || []), entry ]

}), {}); 

const aggregate = (arr, key, reducers) =>

  Object.entries(groupBy(arr, key))

    .map(([k1, values]) => Object.entries(reducers)

      .reduce((obj, [k2, { fn, initial }]) => ({

        ...obj,

        [k2]: values.reduce((acc, item, index, all) =>

          fn(acc, item[k2], index, all), initial || 0)

      }), { [key]: k1 }))

const data = [ 

 { "sku": 123, "val": 10, "val2": 2 },

 { "sku": 124, "val": 12, "val2": 5  },

 { "sku": 123, "val": 20, "val2": 8  }

];

const aggregated = aggregate(data, 'sku', {

  'val'  : { fn: (acc, val) => acc + val, initial: 0 },

  'val2' : { fn: (acc, val) => acc * val, initial: 1 }

});

console.log(aggregated);

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Answer 3

跟踪对象中的总和：

const arr = [ 

    {"sku": 123, "val": 10},

    {"sku": 124, "val":12},

    {"sku": 123, "val": 20}

];

const sums = {};

for (const {sku, val} of arr) {

    if (!(sku in sums)) {

        sums[sku] = 0;

    }

    sums[sku] += val;

}

const result = Object.entries(sums).map(([k, v]) => ({sku: k, val: v}));

console.log(result);

Answer 4

用于forEach构建一个带有键sku和值进行聚合的对象。从上面的对象中

获取。Object.values

const group = (arr) => {

  const res = {};

  arr.forEach(({sku, val}) => {

    res[sku] ? (res[sku].val += val) : res[sku] = { sku, val };

  });

  return Object.values(res);

};

const arr = [

  { sku: 123, val: 10 },

  { sku: 124, val: 12 },

  { sku: 123, val: 20 },

];

console.log(group(arr));