1，引入dhtmlXTreeObject的css和js文件

注意： js的引用顺序很关键！！！

2，创建一棵目录树

2.1，let tree = new dhtmlXTreeObject(id-dhtmltree-0, “100%”, “100%”, 0);

2.2，设置图片根目录（后续使用到的图片都是相对于该目录的）

tree.setImagePath("/common/dhtmlxTree/imgs/");

3，代码

            let tree = new dhtmlXTreeObject(`id-dhtmltree-${this.groupId}`, "100%", "100%", 0);
            tree.setImagePath("/common/dhtmlxTree/imgs/");
            //tree.enableCheckBoxes(1);
            let jsonobj = {
                id:0, 
                item:[
                    {
                        id:1,
                        text:"root",
                        im0:"common/dhtmlxtree_icon.gif",
                        im1:"common/dhtmlxtree_icon.gif",
                        im2:"common/dhtmlxtree_icon.gif",
                        item:[
                            {id:2,text:"first"},
                            {id:3, text:"middle", 
                                item:[
                                    {id:"31", text:"child"}
                                ]},
                            {id:4,text:"last"}
                        ]
                    }
                ]
            }
            console.log(tree)
            tree.loadJSONObject(jsonobj, function(){
                console.log("load json to tree success!")
            });