获取对象数组中没有出现的计数 [英] Fetch the count for no of occurence in a array of object

问题描述

var json = [{
        "city": "California",
        "name": "Joe",
        "age": 17
    }, {
        "city": "California",
        "name": "Bob",
        "age": 17
    }, {
        "city": "California",
        "name": "Bob",
        "age": 35
    }, {
        "city": "Texas",
        "name": "Bob",
        "age": 35
    }, {
        "city": "Florida",
        "name": "Bob",
        "age": 35
    }
];

我只是根据城市价值而没有发生过，即如下所示.

I just to no of occurence based on city value i.e output as below.

updatedjson=[{"name":"California","count":3},{"name":"Texas","count":1},{"name":"Florida","count":1}]

使用lodash或javascript使用任何方法

using any approah using lodash or javascript

推荐答案

使用Lodash，即:

Using Lodash, that would be:

const updatedJson = _(json)
                     .countBy('city')
                     .map((count, name) => ({ name, count }))
                     .value();

const json = [{"city":"California","name":"Joe","age":17},{"city":"California","name":"Bob","age":17},{"city":"California","name":"Bob","age":35},{"city":"Texas","name":"Bob","age":35},{"city":"Florida","name":"Bob","age":35}];

const updatedJson = _(json)
  .countBy('city')
  .map((count, name) => ({ name, count }))
  .value();
  
console.log(JSON.stringify(updatedJson));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js"></script>

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