如何通过操作特定键从对象创建 hashmap

Question

尝试了几天来操纵一些 JSON 数据响应。如何从以下创建哈希图？

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

用于搜索"volvo, opel, honda。解析后，它会返回每个索引的用户，看起来像这样（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

您可以减少数组并使用对象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
  })
}

<script src="https://codepen.io/synthet1c/pen/KyQQmL.js"></script>

Answer 2

使用 ES5

Reduce 数组，并使用辅助对象通过用户名设置对创建对象的引用：

var data = [{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"}];

var helper = {};
var result = data.reduce(function(r, o) {    
  if(!helper[o.user]) {
    helper[o.user] = {};
    r.push(helper[o.user]);
    helper[o.user][o.user] = [];
  }
  
  helper[o.user][o.user].push(o.score);
  
  return r;
}, []);

console.log(result);

使用 ES6

Reduce数组变成Map，然后spreadMap的values返回数组：

const data = [{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 result = [...data.reduce((m, { user, score }) => {  
  const scores = m.get(user) || { [user]: [] };
  
  scores[user].push(score);
  
  return m.set(user, scores);
}, new Map()).values()];

console.log(result);

Answer 3

这是一个普通的旧 JS 方法，没有 map、reduce 或东西

const data = [{"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"}];

let res = []
data.forEach((item) => {
  if (res.length === 0) {
    res.push({[[item.user]]: [item.score]})
  }else {
    let index = -1;
    res.some((obj, i) => {
      if (Number(Object.keys(obj)[0]) === item.user) {
        index = i
        return true;
      }
      return false;
    })
    if (index !== -1) {
      res[index][item.user].push(item.score)
    } else {
      res.push({[item.user]: [item.score]})	
    }
  }
})

console.log(res)