javascript减少数组中对象的多个键

Question

我有以下类型的对象映射(下面的示例数据)

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

我需要将数组缩减为一个包含金额总和和平均价格的对象

我已经阅读了几篇关于如何减少对象上的数据的文章，例如

How to map and reduce over an array of objects?

Javascript reduce on array of objects

在我的例子中，“类型”是 ["PV","BHKW","FALLBACK"] 的枚举，但它可以扩展。除了为 in 循环编写声明之外，我想不出如何使用 array.reduce 来更优雅地完成此任务。

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 data 对象的每个值。要组合具有相同键值的所有对象，您可以使用 lodash#mergeWith使用回调测试是否将评估正在转换的键。

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}

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