Javascript/ES2015，计算出现次数并将其存储为数组中的对象

Question

我正在从 JSON feed 中提取数据，并尝试计算每个名称 (name_class) 出现的次数。

我想返回以下格式的对象数组，其中 count 指名称出现的次数:

myArray = [{name:"John", count: 5}, {name: "Sarah", count: 2}, {name: "Oliver", count: 3}];

到目前为止，我有以下内容，但这不会计算出现的次数，它只是将另一个对象添加到数组中；

   let namestUi = {
    renderNames(names){
        var counter2 = [];
        let namesFound = names.map((name) => {
          let {name_class} = name;

            if(counter2.name == name_class){
              counter2.count++;
            } else { counter2.push({name: name_class, count: 1}); }
        });
        console.log(counter2);
        return namesFound;
      }
    };

这是构建对象数组，但不计算出现的次数。

Answer 1

function count(names){
    // Count occurrences using a map (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map)
    let map = new Map();
    for (let name of names) {
        map.set(name, (map.get(name) || 0) + 1);
    }

    // Transform to array of { name, count }
    let result = [];
    for (let [name, count] of map) {
        result.push({name: name, count: count});
    }

    return result;
}

count(["a", "b", "c", "a", "b", "a"])
// [{"name":"a","count":3},{"name":"b","count":2},{"name":"c","count":1}]