js 合并数组对象中的相同项，并统计数量和

let list=[
  {
    id:11,
    name:'apple',
    num:2
  },
   {
    id:11,
    name:'apple',
    num:3
  },
   {
    id:22,
    name:'pig',
    num:2
  },
   {
    id:11,
    name:'apple',
    num:2
  },
]
list = list.reduce((obj, item) => {  
  let find = obj.find(i => i.id === item.id)  
 let _d = {  
    ...item,  
    frequency: 1  
  }  
  find ? (find.num+=item.num,find.frequency++ ): obj.push(_d)  
  return obj  
}, [])
 
 
//输出
[
  {
    id: 11,
    name: "apple",
    frequency:3,
    num: 7
  },{
    id: 22,
    name: "pig",
    frequency:1,
    num: 2,
  }
]

https://blog.csdn.net/fu_miao_qi_lai/article/details/134268648?ops_request_misc=&request_id=&biz_id=102&utm_term=%E5%90%88%E5%B9%B6%20%E6%95%B0%E7%BB%84%E4%B8%AD%20%E7%9B%B8%E5%90%8C%20%E5%85%83%E7%B4%A0%20%E5%B9%B6%E7%BB%9F%E8%AE%A1%E6%AC%A1%E6%95%B0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~sobaiduweb~default-0-134268648.142^v102^pc_search_result_base7&spm=1018.2226.3001.4187