javascript - 如何通过数组中的键计算相同对象的数量？

Question

我有一个对象数组：

[
  { appleID: 13, bananaID: 55 },
  { appleID: 24, bananaID: 13}, 
  { appleID: 97, bananaID: 13},
  { appleID: 13, bananaID: 55 }
]

结果应如下所示：

[
  { appleID: 13, bananaID: 55, count: 2 },
  { appleID: 24, bananaID: 13, count: 1}, 
  { appleID: 97, bananaID: 13, count: 1}
]

计算相同元素的数量element === appleID && element === bananaID

标签： javascriptarrayssortingobjectjavascript-objects

Answer 1

您可以.reduce通过以下两件事来汇总您的数据：

1. 关键思想是key使用类似的格式构建const key = ${appleID}-${bananaID}
2. 使用 在性能方面，您可以使用object以获得最高的性能（Find just takes O(1)）

   const data = [
     { appleID: 13, bananaID: 55 },
     { appleID: 24, bananaID: 13}, 
     { appleID: 97, bananaID: 13},
     { appleID: 13, bananaID: 55 }
   ];
   
   const result = data.reduce((acc, {appleID, bananaID}) => {
     const key = `${appleID}-${bananaID}`
     acc[key] ??= {appleID, bananaID, count: 0};
     acc[key]["count"] += 1;
     
     return acc;
   }, {});
   
   console.log(Object.values(result));