javascript - 如何在 Javascript 中的 Map 中添加对象数组

Question

我想要一个 Map，其中键是唯一 id，值将是与唯一 id 对应的对象数组。示例数据

const exampleData = [
{id: 1,
name: "Tony",
},
{id: 2,
name: "Lori"
},
{id: 2,
name: "Pete"
},
{id: 2,
name: "Brandon"
},
];

这是我尝试过的

let map = new Map();
filteredArray.map(array => {
  map.set(array.assessmentId, [...map.get(array.assessmentId), array]); 
});

我想要的结果：

Map (
[key: 1,
value: [id: 1, Name: Tony],
],
[key:2,
value:[id: 2, Name: Lori],[id: 2, Name: Pete], [id: 2, Name: Brandon]
])

标签： javascript

Answer 1

如果要对数据进行分组，可以减少项目并将每个项目连接到由id属性键控的数组。

const data = [
  { id: 1, name: "Tony", },
  { id: 2, name: "Lori" },
  { id: 2, name: "Pete" },
  { id: 2, name: "Brandon" },
];

const grouped = new Map(Object.entries(data.reduce((result, item) => ({
  ...result,
  [item.id]: [ ...(result[item.id] || []), item ]
}), {})));
  
console.log(...grouped);

.as-console-wrapper { top: 0; max-height: 100% !important; }

输出

{
  "1": [
    { "id": 1, "name": "Tony" }
  ],
  "2": [
    { "id": 2, "name": "Lori" },
    { "id": 2, "name": "Pete" },
    { "id": 2, "name": "Brandon" }
  ]
}

这是一个可重用的功能：

const groupDataByKey = (data, key) =>
  new Map(Object.entries(data.reduce((result, item) => ({
    ...result,
    [item[key]]: [ ...(result[item[key]] || []), item ]
  }), {})));
  
const exampleData = [
  { id: 1, name: "Tony", },
  { id: 2, name: "Lori" },
  { id: 2, name: "Pete" },
  { id: 2, name: "Brandon" },
];

console.log(...groupDataByKey(exampleData, 'id'));

.as-console-wrapper { top: 0; max-height: 100% !important; }