js 实现 list转换成tree的方法示例（数组到树）

const oldData = [  {id:1,name:'boss',parentId:0},  {id:2,name:'lily',parentId:1},  {id:3,name:'jack',parentId:1},  {id:4,name:'john',parentId:2},  {id:5,name:'boss2',parentId:0},]function listToTree(oldArr){  oldArr.forEach(element => {    let parentId = element.parentId;    if(parentId !== 0){      oldArr.forEach(ele => {        if(ele.id == parentId){ //当内层循环的ID== 外层循环的parendId时，（说明有children），需要往该内层id里建个children并push对应的数组；          if(!ele.children){            ele.children = [];          }          ele.children.push(element);        }      });    }  });  console.log(oldArr) //此时的数组是在原基础上补充了children;  oldArr = oldArr.filter(ele => ele.parentId === 0); //这一步是过滤，按树展开，将多余的数组剔除；  console.log(oldArr)  return oldArr;}listToTree(oldData);