Vue component library ElementUI implements table loading tree data tutorial

<el-table
  ref="Table"
  :data="apprItemData"
  :header-cell-style="headClass"
        @select="handleSelection"
        row-key="approveItem"
        height="420"
  border
       default-expand-all
       :tree-props="{children: 'children'}">
 <el-table-column
   type="selection"
   width="55">
 </el-table-column>
 <el-table-column
   prop="itemCode"
   label="Item code">
 </el-table-column>
 <el-table-column
   prop="approveName"
   label="Item Name">
 </el-table-column>
 <el-table-column
   prop="apprStatusStr"
   label="Configuration link"
   color="blue">
 </el-table-column>
</el-table>

{
    "id":3,
    "itemCode":"123",
    "approveName":"Test items",
    "apprStatusStr":"Link Name",
    "children":[
        {
            "id":31,
            "itemCode":"111",
            "approveName":"Test items",
            "apprStatusStr":"Link name"
        }
    ]
}

<script type="text/babel">
       var vm = new Vue({
           el: '#app',
           data:{
               apprItemData : [],
               currentPage: 1, //Current page totalRow: 0, //Total number of pages pageSize: 10 //Current number of displayed items},
           computed: {},
           watch: {},
           created() {},
           mounted() {
               this.loadItemData();
  },
           methods: {
               // Load item information loadItemData () {
                   var pageSize = this.pageSize;
                   var currentPage = this.currentPage;
                   console.log("pageSize:"+pageSize+",currentPage:"+currentPage);
       //debugger;
       var geturl = '${root}/config/loadItemData.do?rows='+pageSize + '&page=' + currentPage;
                   $.ajax({
                       type: 'get',
                       url:geturl,
                       contentType: "application/json; charset=utf-8",
                       success: function(data) {
                           //debugger;
                           console.log("totalRow:"+data.total);
                           vm.apprItemData = data.rows;
                       },
                       error: function(e) {
                           console.log("Error in updating data:",e);
                       }
                   })
               }
           }
       });
</script>