javascript - 如何通过操作特定键从对象创建 HashMap

Question

尝试了几天来操作一些 JSON 数据响应。如何根据以下内容创建 HashMap ？

var jsonObject = JSON.parse(xhr.responseText); //response that parced

用于搜索“volvo、opel、honda。解析后，它返回每个用户的索引，如下所示(jsonObject.length在每个不同的搜索中都会发生变化):

[{user: 1, car: volvo, score:7, time: "some time"},{user: 2, car: volvo, score:8, time: "some time"},{user: 3, car: volvo, score:9, time: "some time"},{user: 3, car: opel, score:6, time: "some time"},{user: 3, car: honda, score:8, time: "some time"},{user: 4, car: volvo, score:6, time: "some time"},{user: 4, car: opel, score:7, time: "some time"},{user: 5, car: honda, score:8, time: "some time"}]

我希望输出是这样的:

[{1:[7]},{2:[8]},{3:[9,6,8]},{4:[6,7]},{5:[8]}]

Answer 1

您可以使用一个对象来减少数组并收集每个用户的所有分数，以确保您拥有唯一的用户 ID 作为键

const jsonObject = [
  {user: 1, car: 'volvo', score:7, time: "some time"}
, {user: 2, car: 'volvo', score:8, time: "some time"}
, {user: 3, car: 'volvo', score:9, time: "some time"}
, {user: 3, car: 'opel', score:6, time: "some time"}
, {user: 3, car: 'honda', score:8, time: "some time"}
, {user: 4, car: 'volvo', score:6, time: "some time"}
, {user: 4, car: 'opel', score:7, time: "some time"}
, {user: 5, car: 'honda', score:8, time: "some time"} 
]

const results = jsonObject.reduce((map, obj) => {
  // set a new key based on the user id if it doesn't exist
  if (!map.has(obj.user)) {
    map.set(obj.user, [])
  }
  // add to the users scores to the users score
  map.get(obj.user).push(obj.score)
  // return the accumulator
  return map
}, new Map)

for (let [key, value] of results.entries()) {
  console.log({
    key,
    value
  })
}

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