javascript - 比较两个玩家分数数组，看看谁在列表中上升/下降

Question

我有两个在不同时间段拍摄的数组。如何通过将新玩家标记为上升来检查哪些玩家在列表中上升/下降？

附言- 数组已经根据分数排序。

pastData:[
  
    {
    playerName:'John Doe',
    score:50
    },
    {
    playerName:'Jane Doe',
    score:40
    },
    {
    playerName:'John Appleseed',
    score:30
    },
    {
    playerName:'John Walker',
    score:20
    },
  ]

presentData:[

    {
    playerName:'Jane Doe',
    score:80
    },
    {
    playerName:'John Doe',
    score:60
    },
    {
    playerName:'John Appleseed',
    score:40
    },
    {
    playerName:'John Mayer',
    score:30
    },
  ]

我需要检查比较两个数组的索引变化并获得如下输出。

   presentData:[

    {
    playerName:'Jane Doe',
    score:80,
    position:'up'
    },
    {
    playerName:'John Doe',
    score:60,
    position:'down'
    },
    {
    playerName:'John Appleseed',
    score:40,
    position:'same'
    },
    {
    playerName:'John Mayer',
    score:30,
    position:'up'
    },
  ]

我正在尝试如下，但似乎无法为新播放器用例找到解决方案。

let status=[] //this array will include the changes 
which I can use later to update the presentData array 
with a "position:'up/down/same'" key-value pairs.

for (let i = 0; i < 4; i++) { 

  for(let j=0; j<4; j++) {

   if(Object.values(pastData)[i].id==Object.values(presentData)[j].id){
     if(i==j){
      status.push('same')

     }
     if(i<j){
      status.push('down')

      }
     if(i>j){
       status.push('up')
     }
   }

  }

  

}

Answer 1

1. 创建 Map从将 playerName 映射到他们的 index 的 pastData 数组中。

2. 遍历 presentData 数组并使用 map 计算每个玩家的位置。

const pastData = [
  { playerName: "John Doe", score: 50 },
  { playerName: "Jane Doe", score: 40 },
  { playerName: "John Appleseed", score: 30 },
  { playerName: "John Walker", score: 20 },
];

const presentData = [
  { playerName: "Jane Doe", score: 80 },
  { playerName: "John Doe", score: 60 },
  { playerName: "John Appleseed", score: 40 },
  { playerName: "John Mayer", score: 30 },
];

const pastDataMap = new Map(pastData.map((d, i) => [d.playerName, i]));

const status = presentData.map((d, i) => {
  const pastIndex = pastDataMap.get(d.playerName);
  return {
    ...d,
    position:
      pastIndex === undefined || i < pastIndex
        ? "up"
        : i > pastIndex
        ? "down"
        : "same",
  };
});

console.log(status);

其他相关文件:

• Spread syntax (...)
• Array.prototype.map