javascript - 获取对象数组中出现次数的计数

Question

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
    }
];

我只是为了不发生基于城市值(value)的事件，即输出如下。

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

使用任何使用 lodash 或 javascript 的方法

Answer 1

使用 Lodash，这将是:

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));

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