如何计算 Javascript 对象数组中不同值出现的次数? [英] How to count number of occurrences of distinct values from an array of objects in Javascript?

问题描述

我有一个像下面这样的对象数组:

I have an array of objects like below:

var array =
    [
        {"name":"abc","age":20}
        {"name":"abc","age":20}
        {"name":"abc","age":20}
        {"name":"xyz","age":21}
        {"name":"xyz","age":21}
    ]

我想计算不同值的出现次数，例如:

I want to count the number of occurrences of distinct values like:

[3,2]

假设 abc 出现 3 次，xyz 出现 2 次.

Assuming abc has 3 occurrences and xyz has 2 occurrences.

我在 reactjs 中做这件事.我能够使用 这个答案.

I am doing it in reactjs. I am able to get distinct values like [abc,xyz] using this answer.

_{首选 ES6 语法.}

推荐答案

你需要知道一个计数属于哪个名字，所以我建议不要输出一个不给你任何线索的数组，而是一个键控的对象按名称和相应的计数作为值:

You'll need to know to which name a count belongs, so I propose not to output an array that gives you no clue about that, but an object keyed by names and with as value the corresponding count:

var result = array.reduce( (acc, o) => (acc[o.name] = (acc[o.name] || 0)+1, acc), {} );

var array =
    [
        {"name":"abc","age":20},
        {"name":"abc","age":20},
        {"name":"abc","age":20},
        {"name":"xyz","age":21},
        {"name":"xyz","age":21}
    ];
    
var result = array.reduce( (acc, o) => (acc[o.name] = (acc[o.name] || 0)+1, acc), {} );

console.log(result);

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