整理一个javascript对象数组[重复]

Question

我正在处理的特定数据操作的措辞很困难，所以请原谅这个糟糕的标题 - 我会举一个很好的例子。我有以下 javascript 对象数组，其中包含一些运动数据：

[
    { team: "Knicks", assists: 24 }, 
    { team: "Knicks", assists: 12 }, 
    { team: "Knicks", assists: 17 }, 
    { team: "Knicks", assists: 19 }, 
    { team: "Warriors", assists: 31 }, 
    { team: "Warriors", assists: 25 }, 
    { team: "Warriors", assists: 20 }, 
    { team: "Spurs", assists: 15 }, 
    { team: "Spurs", assists: 17 }, 
    { team: "Spurs", assists: 32 }, 
    { team: "Spurs", assists: 12 }, 
    { team: "Spurs", assists: 18 }
]

并且想整理一下，使数据看起来像这样：

[
    { team: "Knicks", assists: [24, 36, 53, 72] },
    { team: "Warriors", assists: [31, 56, 76] },
    { team: "Spurs", assists: [15, 32, 64, 76, 94] }

]

原始对象数组中的每个唯一团队都会在新数组中接收自己的对象，而助攻值现在是助攻值的累积总和。我相当肯定，原始对象数组总是以正确的方式排序，这样从上到下循环将产生正确的累积和。

非常感谢任何帮助，谢谢！

Answer 1

您可以使用reduce 方法构建一个对象，然后使用Object.values 方法获取对象数组。

const data = [{"team":"Knicks","assists":24},{"team":"Knicks","assists":12},{"team":"Knicks","assists":17},{"team":"Knicks","assists":19},{"team":"Warriors","assists":31},{"team":"Warriors","assists":25},{"team":"Warriors","assists":20},{"team":"Spurs","assists":15},{"team":"Spurs","assists":17},{"team":"Spurs","assists":32},{"team":"Spurs","assists":12},{"team":"Spurs","assists":18}]

const result = data.reduce((r, {team, assists}) => {
  if(!r[team]) r[team] = {team, assists: [assists]}
  else r[team].assists.push(r[team].assists.slice(-1)[0] + assists);
  return r;
}, {})

console.log(Object.values(result))

Answer 2

你也可以像这样使用 array#forEach() 方法：

const teams= [
    { team: "Knicks", assists: 24 }, 
    { team: "Knicks", assists: 12 }, 
    { team: "Knicks", assists: 17 }, 
    { team: "Knicks", assists: 19 }, 
    { team: "Warriors", assists: 31 }, 
    { team: "Warriors", assists: 25 }, 
    { team: "Warriors", assists: 20 }, 
    { team: "Spurs", assists: 15 }, 
    { team: "Spurs", assists: 17 }, 
    { team: "Spurs", assists: 32 }, 
    { team: "Spurs", assists: 12 }, 
    { team: "Spurs", assists: 18 }
]

let teamGroup = {}

teams.forEach(team => {
  teamGroup[team.team] ? // check if that array exists or not in teamgroup object
    teamGroup[team.team].push(team.assists)  // just push
   : (teamGroup[team.team] = [], teamGroup[team.team].push(team.assists)) // create a new array and push
})

console.log(teamGroup);

Answer 3

这是函数式编程方法，使用临时 ES6 Map：

const teams = [{ team: "Knicks", assists: 24 },{ team: "Knicks", assists: 12 },{ team: "Knicks", assists: 17 },{ team: "Knicks", assists: 19 },{ team: "Warriors", assists: 31 },{ team: "Warriors", assists: 25 },{ team: "Warriors", assists: 20 },{ team: "Spurs", assists: 15 },{ team: "Spurs", assists: 17 },{ team: "Spurs", assists: 32 },{ team: "Spurs", assists: 12 },{ team: "Spurs", assists: 18 }];

const result = Array.from(
    teams.reduce( (acc, {team, assists}) => acc.set(team, (acc.get(team) || []).concat(assists)), new Map),
    ([team, assists]) => ({team, assists})
);

console.log(result);

Answer 4

lodash 库有一个方便的 _.groupBy 可以为您完成相当多的工作。

如果你这样做const groups = _.groupBy(data, team)，你会得到：

{
    "Knicks": [
        { "team": "Knicks", "assists": 24},
        { "team": "Knicks", "assists": 12},
        { "team": "Knicks", "assists": 17},
        { "team": "Knicks", "assists": 19},
    ],
    // ...
}

那么，

const result = _.map(groups, (teamData, teamName) => {
    // Convert teamData array into a single record
    const assists = _.map(teamData, "assists"); // e.g. [24, 12, 17, 19]
    return { team: teamName, assists: runningTotal(assists) };
});

// Turns an array like [1,2,3,4] into an array like [1,3,6,10]
function runningTotal(array) {
    let prev = 0;
    return array.map(next => {
        prev = next + prev;
        return prev;
    });
}

这给出了预期的结果。

---

这种方法并不比使用reduce 的解决方案短很多，但我个人发现像groupBy 和map 这样的高阶运算比reduce 更容易推理。 （当然，这需要 lodash 或类似实现的 groupBy 函数）

---

编辑：我完全错过了助攻不仅仅是一系列助攻，而是一个运行总数。增加了一点来解释这一点。代码比 reduce 解决方案长得多，但 IMO 更清晰。