js如何构造elementUI树状菜单的数据结构详解

var treeData={
        id: 1,
        label: '一级 1',
        newVal: "",
        children: [{
          id: 4,
          label: '二级 1-1',
          newVal: "",
          children: [{
            id: 9,
            label: '三级 1-1-1',
            newVal: "",
          }, {
            id: 10,
            label: '三级 1-1-2',
            newVal: "",
            children:[{
              id: 4444,
            label: '四级 1-1-1-4',
            newVal: "",
            }]
          }]
        },{
          id:22,
          label:'二级 22',
          newVal:''
        }]
      }

var itemlist =[
        {itemCode:'11', itemName:'材料11',itemType:'2',parentPk:'1'},
        {itemCode:'111', itemName:'材料111',itemType:'3',parentPk:'11'},  
        {itemCode:'1111', itemName:'材料1111',itemType:'3',parentPk:'111'},
        {itemCode:'1112', itemName:'材料1112',itemType:'3',parentPk:'111'} 
      ]

//root节点
全局对象，因为不同的递归执行，要访问的一个tree对象
var itemtree ={
    id:'1',
    label:'物料名称_整机',
    children:[]
}

//数据库返回的菜单list
全局对象，因为不同的递归执行，要访问的一个list对象
var itemlist =[
        {itemCode:'11', itemName:'材料11',itemType:'2',parentPk:'1'},
        {itemCode:'12', itemName:'材料12',itemType:'2',parentPk:'1'},
        {itemCode:'111', itemName:'材料111',itemType:'3',parentPk:'11'},  
        {itemCode:'1111', itemName:'材料1111',itemType:'3',parentPk:'111'},
        {itemCode:'1112', itemName:'材料1112',itemType:'3',parentPk:'111'} 
      ]

function buildtree(itemtreenode,itemlist){
  if (itemlist.length===0) {
    console.log('条件结束')
    return 
  }
  var j=0   /*！！注意循环变量j必须定义为局部变量，否则默认全局变量，会导致子节点丢失*/
//   var len=0
  for(j=0,len=itemlist.length;j<len;j++){
    console.log(new Date(),'j==>:',j,'len==>:',len,itemtreenode,itemlist)
    if (itemtreenode.id===itemlist[j].parentPk){
      var node={id:itemlist[j].itemCode,label:itemlist[j].itemName,children:[]}
      itemtreenode.children.push(node)    
//       itemlist.splice(j,1)  /*!! 没有删除list元素，否则会导致后续引用错误。代码不是很完美，一时没想到完美方法*/
      buildtree(node,itemlist)      
  }    
  
}
  console.log('循环结束')
}

console.log('begin')
buildtree(itemtree,itemlist)  
console.log(itemtree)

var treeData={
        id: 1,
        label: '一级 1',
        newVal: "",
        children: [{
          id: 4,
          label: '二级 1-1',
          newVal: "",
          children: [{
            id: 9,
            label: '三级 1-1-1',
            newVal: "",
          }, {
            id: 10,
            label: '三级 1-1-2',
            newVal: "",
            children:[{
              id: 4444,
            label: '四级 1-1-1-4',
            newVal: "",
            }]
          }]
        },{
          id:22,
          label:'二级 22',
          newVal:'',
          children:[{id:'2-2-1',label:'三级221',newVal:'',children:[],}]
        }]
      }

var exp=undefined

var itemlist=[]
function tree2list(itemnode){
  if(typeof(itemnode)=="undefined"){
    console.log('返回：',itemnode)
    return
  }
  
  if(itemnode.children && itemnode.children.length>0){
  	var i=0  
    for(i=0;i<itemnode.children.length;i++){
      itemnode.children[i].parentPk=itemnode.id
      console.log(itemnode.children[i])
      itemlist.push(itemnode.children[i])       
      this.tree2list(itemnode.children[i])
    }
  }
}
 

console.log('begin')
tree2list(treeData,itemlist)
console.log(itemlist)