js多个组数取交集

let resdata=[
  {name:'我是1',trend:[{value:1,date:20210901},{value:2,date:20210902},{value:2,date:20210903},{value:2,date:20210904}]},
  {name:'我是2',trend:[{value:2,date:20210902},{value:2,date:20210903},{value:2,date:20210904}]},
  {name:'我是3',trend:[{value:1,date:20210901},{value:2,date:20210902},{value:2,date:20210903},{value:2,date:20210904},{value:1,date:20210905}]},
  {name:'我是4',trend:[{value:10,date:20210901},{value:11,date:20210903},{value:13,date:20210904},{value:1,date:20210905}]}
]
let example=[],xdata=[]
for (let i = 0; i < resdata.length; i++) {
  let obj={index:i,len:resdata[i].trend.length}
  example.push(obj)
}
let indenb=example.sort(function(a,b){return a.len-b.len})[0].index;
xdata=resdata[indenb].trend
let map = new Map()
xdata = xdata.map(item => {
  map.set(item.date, item.value)
  return item.date
})
//  满足 N 个数组同时有这个时间, 再 除以 第一项 => 存储
let seriesData = []
resdata.forEach(v => {
  let obj = {
    name: v.name,
    data: []
  }
  v.trend.forEach(item => {
    if (map.get(item.date)) {
      obj.data.push(item)
    }
  })
  seriesData.push(obj)
})