array.map( x => f(x) )这将遍历数组的元素，并返回一个新数组，其元素为f(x)

const data = [
  {
    "id": { "server": "xxxxx", "user": "123456", "_serialized": "64566" },
    "name": "Doe",
    "isCalled": false,
    "isReceived": false,
    "unreadCount": 1
  },
  {
    "id": {
      "server": "xxxxx",
      "user": "123456",
      "_serialized": "64566"
    },
    "name": "Doe",
    "isCalled": false,
    "isReceived": false,
    "unreadCount": 1
  },
  {
    "id": {
      "server": "xxxxx",
      "user": "123456",
      "_serialized": "64566"
    },
    "name": "Doe",
    "isCalled": false,
    "isReceived": false,
    "unreadCount": 1
  }
]

const newData = data.map(d => ({ "user": d.id.user }));

console.log(newData)

您可以将Array.prototype.map()与destructuring assignment结合使用

const data = [{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1,},{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1,},{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1}]

const result = data.map(({ id: { user } }) => ({ user }))

console.log(result)

Array#map（参见@YosvelQuintero的答案）是最好的方法。在这里我将说明您也可以使用Array#reduce方法：

const 
    data = [{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1,},{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1,},{id: {server: 'xxxxx',user: '123456',_serialized: '64566',},name: 'Doe',isCalled: false,isReceived: false,unreadCount: 1}],

    output = data.reduce(
        (acc, { id: { user } }) => [...acc,{ user }],[]
    );

console.log( output );