js 树的各种骚操作，生成树，父子链，树推平

js生成树结构

1、假树，利用共享内存实现，非真遍历，这个是一种比较直观的写法

      let list = [
        {id:1,name:100},
        {id:11,name:101,pid:1},
        {id:111,name:1011,pid:11},
        {id:2,name:200},
        {id:22,name:202,pid:2},
        {id:3,name:3002},
        {id:32,name:3003,pid:1},
        {id:42,name:4003,pid:111}
      ]
      let mapList = list.reduce((prev,v)=>{
        prev[v.id]=v
        return prev
      },[])
      let tree = list.reduce((prev,v)=>{
        if(!mapList[v.pid]){
          v.children?'':(v.children=[])
          prev=[...prev,...[v]]
        }else{
          mapList[v.pid].children?'':(()=>mapList[v.pid].children=[])()
          mapList[v.pid].children=[...mapList[v.pid].children,...[v]]
        }
        return prev
      },[])
      console.log(mapList);
      console.log(tree);

2.假树， 同第一种原理，非直观写法,是不是简便多了

 let tree = list.map(v=>{
        v.children?'':(()=>v.children=[])()
        v.pid?'':(()=> v.type='parent')()
        v.children = list.filter(m=>m.pid===v.id)
        return v
      }).filter(v=>v.type==='parent')
      console.log(list);
      console.log(tree);

级联数据拉平
  //级联数据拉平
function  flatArray(key,deep,arr){
    const readNodes =  function(key,deep,arr,data=[]){
      for (let item of arr) {
          data.push(item)
          if (item[deep] && item[deep].length){
            readNodes(key,deep,item[deep],data)
          }
       }
       return data
    }
    return readNodes(key,deep,arr)
  }
flatArray('id','children',list）
返回父子链

function findParent(value,key,parent,deep,arr1=[]){
  let readNodes = (value,key,parent,deep,arr,data=[])=>{
    for(let v of arr){
      if(!value) break
      if(v[key]===value){
        data.unshift(v)
        readNodes(v[parent],key,parent,deep,arr1,data)
        break
      }else{
        v[deep]&&v[deep].length?readNodes(value,key,parent,deep,v[deep],data):''
      }
    }
    return data
  }
  return readNodes(value,key,parent,deep,arr1)
}

console.log(findParent(111,'id','pid','children',tree));

作者：沧桑岁月歌
链接：https://www.jianshu.com/p/59a941b5bd8e
来源：简书
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