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json - 在 JSON 中查找列表中项目的出现次数

问题描述

我一直在关注我拥有他们汽车制造商的 JSON。lodash 中是否有更好的方法可以从预定义的列表中获取汽车制造商的数量。

例如，

{
    "data": [
        {"ownerId":"00001", "make": "Honda"},
        {"ownerId":"00002", "make": "Nissan"},
        {"ownerId":"00003", "make": "Audi"},
        {"ownerId":"00004", "make": "Porsche"},
        {"ownerId":"00005", "make": "Honda"},
        {"ownerId":"00006", "make": "Honda"},
        {"ownerId":"00007", "make": "Audi"},
        {"ownerId":"00008", "make": "Volkswagen"},
        {"ownerId":"00009", "make": "Honda"},
        {"ownerId":"00010", "make": "Porsche"},
        {"ownerId":"00011", "make": "Volkswagen"}
    ]
}

计算计数的过滤器列表：

["Honda", "Audi", "Porsche"]

预期结果：

[{"Audi": 2}, {"Honda": 4}, {"Porsche": 2}]

输入 JSON 中还有其他汽车制造商，但由于过滤器列表没有，因此未考虑。

标签： jsonlodash

解决方案

您可以使用_.countBy()获取每个品牌的计数和对象，然后_.pick()是您想要的项目：

const cars = {"data":[{"ownerId":"00001","make":"Honda"},{"ownerId":"00002","make":"Nissan"},{"ownerId":"00003","make":"Audi"},{"ownerId":"00004","make":"Porsche"},{"ownerId":"00005","make":"Honda"},{"ownerId":"00006","make":"Honda"},{"ownerId":"00007","make":"Audi"},{"ownerId":"00008","make":"Volkswagen"},{"ownerId":"00009","make":"Honda"},{"ownerId":"00010","make":"Porsche"},{"ownerId":"00011","make":"Volkswagen"}]};

const list = ["Honda", "Audi", "Porsche"];

const result = _.pick(_.countBy(cars.data, 'make'),  ["Honda", "Audi", "Porsche"]);

console.log(result);
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