如何在javascript中的对象数组下获取值重复的计数

Question

我有一个数组，它有一些重复计数。 我想获得重复次数。 我的数组是这样的：

var array = [
    { asset: "A", sector: "Hospital" },
    { asset: "B", sector: "Hardware" },
    { asset: "C", sector: "Networking" },
    { asset: "D", sector: "Networking" },
    { asset: "E", sector: "Food" },
    { asset: "F", sector: "Hospital" },
    { asset: "G", sector: "Hardware" },
    { asset: "H", sector: "Industrial" },
    { asset: "I", sector: "Transport" },
    { asset: "J", sector: "Hardware" },
    { asset: "K", sector: "Networking" },
    { asset: "L", sector: "Transport" }
]

现在我想要重复计数也是这样的排序顺序：

final_array = [
    { sector: 'Hardware', count: 3 },
    { sector: 'Networking', count: 3 },
    { sector: 'Hospital', count: 2 },
    { sector: 'Transport', count: 2 },
    { sector: 'Food', count: 1 },
    { sector: 'Industrial', count: 1 }
]

我不知道从哪里可以做到这一点。 我有很多链接，但他们解决了数组下的重复而不是对象数组。

我使用一种方法，但不能解决我的问题

var finalD = [];
c.forEach(x => {
    if (isSectorExists(x.sector, finalD) == true) {
        //Here I don't know how I will increase the counter.
    } else {
        finalD.push({ sector: x.sector, count: 1 });
    }
});

var isSectorExists = (sector, arr) => {
    return arr.some(function(el) {
        return el.sector === sector;
    });
};

我知道我的方法很长。 有人有最好和最简单的方法来完成这种任务吗？ 任何帮助真的很感激。 提前致谢

Answer 1

您可以构建一个以扇区名称为键的对象counts和一个将计数存储为值的对象，遍历数组并更新这些计数，然后最终获得该counts对象的值。

 var array = [ { asset: "A", sector: "Hospital" }, { asset: "B", sector: "Hardware" }, { asset: "C", sector: "Networking" }, { asset: "D", sector: "Networking" }, { asset: "E", sector: "Food" }, { asset: "F", sector: "Hospital" }, { asset: "G", sector: "Hardware" }, { asset: "H", sector: "Industrial" }, { asset: "I", sector: "Transport" }, { asset: "J", sector: "Hardware" }, { asset: "K", sector: "Networking" }, { asset: "L", sector: "Transport" } ]; var counts = array.reduce((m, c) => { if (c.sector in m) m[c.sector].count += 1; else m[c.sector] = { sector: c.sector, count: 1}; return m; }, {}); let finalArray = Object.values(counts).sort((a, b) => b.count - a.count); console.log(finalArray);

这将在线性时间内获得计数（而不是为每个元素调用isSectorExists使其成为O(n^2) 。