Question

我具有以下类型的Object映射（以下示例数据）

{[date:string]:Array<{[type:string]:{amount:number, price:number}}>}

我需要将数组简化为金额和价格平均的单个对象

我已经阅读了几篇关于如何减少像这样的对象上的数据的帖子

How to map and reduce over an array of objects?

Javascript reduce on array of objects

在我的情况下，“类型”是[[PV]，“ BHKW”，“ FALLBACK”]的ENUM，但可以扩展。除了为in循环编写声明性代码外，我无法弄清楚如何使用array.reduce更优雅地完成此操作。

有什么建议吗？

{
    "2018-08-01T11:00:00+02:00": [
        {
            "BHKW": {
                "amount": 131,
                "price": 85
            },
            "FALLBACK": {
                "amount": 84,
                "price": 1
            }
        },
        {
            "BHKW": {
                "amount": 307,
                "price": 58
            },
            "PV": {
                "amount": 4,
                "price": 60
            }
        }
    ],
    "2018-08-01T12:00:00+02:00": [
        {
            "BHKW": {
                "amount": 288,
                "price": 59
            },
            "PV": {
                "amount": 742,
                "price": 73
            }
        },
        {
            "BHKW": {
                "amount": 250,
                "price": 49
            },
            "PV": {
                "amount": 507,
                "price": 98
            }
        },
        {
            "PV": {
                "amount": 368,
                "price": 22
            },
            "BHKW": {
                "amount": 357,
                "price": 73
            }
        },
        {
            "FALLBACK": {
                "amount": 135,
                "price": 62
            },
            "BHKW": {
                "amount": 129,
                "price": 93
            }
        }
    ],

Answer 1

您可以使用lodash#mapValues转换对象curl --cafile对象的每个值。要将所有具有相同键值的对象组合在一起，可以使用lodash#mergeWith进行回调测试，以评估将要转换的键。

data

const result = _.mapValues(data, collection => 
  _.mergeWith({}, ...collection, (a = 0, b = 0, key) =>
    ['amount', 'price'].includes(key)
      ? a + b
      : void 0 // is equivalent to undefined to retain current value
  ));

const data = {
    "2018-08-01T11:00:00+02:00": [
        {
            "BHKW": {
                "amount": 131,
                "price": 85
            },
            "FALLBACK": {
                "amount": 84,
                "price": 1
            }
        },
        {
            "BHKW": {
                "amount": 307,
                "price": 58
            },
            "PV": {
                "amount": 4,
                "price": 60
            }
        }
    ],
    "2018-08-01T12:00:00+02:00": [
        {
            "BHKW": {
                "amount": 288,
                "price": 59
            },
            "PV": {
                "amount": 742,
                "price": 73
            }
        },
        {
            "BHKW": {
                "amount": 250,
                "price": 49
            },
            "PV": {
                "amount": 507,
                "price": 98
            }
        },
        {
            "PV": {
                "amount": 368,
                "price": 22
            },
            "BHKW": {
                "amount": 357,
                "price": 73
            }
        },
        {
            "FALLBACK": {
                "amount": 135,
                "price": 62
            },
            "BHKW": {
                "amount": 129,
                "price": 93
            }
        }
    ]
};

const result = _.mapValues(data, collection => 
  _.mergeWith({}, ...collection, (a = 0, b = 0, key) =>
    ['amount', 'price'].includes(key)
      ? a + b
      : void 0 // is equivalent to undefined to retain current value
  ));
  
console.log(result);

.as-console-wrapper{min-height:100%;top:0}

Answer 2

解决了！

var x = _.reduce(
    list,
    (acc, item) => {
        for (const key in item) {
            if (!acc[key]) {
                acc[key] = { price: 0, amount: 0 };
            }

            if (item[key] && item[key].price) {
                acc[key].price += item[key].price;
            }

            if (item[key] && item[key].amount) {
                acc[key].amount += item[key].amount;
            }
        }
        return acc;
    },
    {}
);

Answer 3

另一种方法（尽管不如已经发布的_.merge方法那么优雅）是使用_.mapValues/_.reduce/_.assignWith or _.extendWith：

var data = { "2018-08-01T11:00:00+02:00": [{ "BHKW": { "amount": 131, "price": 85 }, "FALLBACK": { "amount": 84, "price": 1 } }, { "BHKW": { "amount": 307, "price": 58 }, "PV": { "amount": 4, "price": 60 } } ], "2018-08-01T12:00:00+02:00": [{ "BHKW": { "amount": 288, "price": 59 }, "PV": { "amount": 742, "price": 73 } }, { "BHKW": { "amount": 250, "price": 49 }, "PV": { "amount": 507, "price": 98 } }, { "PV": { "amount": 368, "price": 22 }, "BHKW": { "amount": 357, "price": 73 } }, { "FALLBACK": { "amount": 135, "price": 62 }, "BHKW": { "amount": 129, "price": 93 } } ] }

var result =
  _.mapValues(data, (x) =>
    _.reduce(x, (r, c) =>
      _.assignWith(r, c, (o, s) =>
        o && s ? ({ amount: o.amount + s.amount, price: o.price + s.price }) : {...o, ...s})
    )
  )

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

javascript减少数组中对象的多个键

3 个答案: