examSystem-Anxin/src/app/http-interceptors/tree.service.ts

import { Injectable } from '@angular/core';

@Injectable()
export class TreeService {
    
    
    toTree(olddata){
        let newdata = []
        function getparentNode(parentId){
            return olddata.find((item)=>{
              return item.id == parentId
            })
          }
        olddata.forEach(item => {
            var parentNode =  getparentNode(item.parentId);
            if(parentNode){
                if(!parentNode.children){
                    parentNode.children = []
                }

                if (parentNode.children.length == 0) {
                    item.isTop = true;
                } else {
                    item.isTop = false;
                    parentNode.children[parentNode.children.length -1].isBottom = false;
                }
                item.isBottom = true;

                parentNode.children.push(item)
            }else{
                if(!item.parentId){//如果parentId为null
                    newdata.push(item)
                }
            }
        });
        return newdata;
    }
}