如何通过数组中的键计算相同对象的数量？ [关闭]

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 }
]

结果应该是这样的：

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

按element === appleID && element === bananaID计算相同元素的个数

Answer 1

您可以使用.reduce 通过以下 2 项来汇总您的数据：

1. 关键思想是使用const key = ${appleID}-${bananaID} 之类的格式构建key
2. 使用在性能方面，可以使用object获得最高性能（查找只需要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));

Answer 2

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

function countNum(arr){
    return arr.reduce((pre, item) => {
        const hasItem = pre.find(subItem => subItem.appleID === item.appleID && subItem.bananaID === item.bananaID)
        if(hasItem){
            hasItem.count++
        }else{
            pre.push({...item, count: 1})
        }
        return pre
    }, [])
}

console.log(countNum(data))

喜欢这个

function countNum(arr){
    return arr.reduce((pre, item) => {
        const hasItem = pre.find(subItem => subItem.appleID === item.appleID && subItem.bananaID === item.bananaID)
        if(hasItem){
            hasItem.count++
        }else{
            pre.push({...item, count: 1})
        }
        return pre
    }, [])
}