element-ui中表格 type="expand"設置全部展開

1、table需要綁定兩個屬性expand-row-key和row-key

 <el-table
      :data="tableData"
      :expand-row-keys="expends"  //expends是數組，設置你要展開行的id
      :row-key="getRowKeys" //通過getRowKeys方法獲取到row的行id值
      >

2、data中設置

 data() {
    return {
      expends:[],
      }
   }

3、methods中設置

 methods: {
    //設置table中的擴展項，展開的id，此處我需要全部展開
    getExpends(){
      var Id = this.tableData.map(item => item.id)
            this.expends = Id
    },
    getRowKeys(row){
      return row.id
    },
    }

4、created()中調用 getExpends()，使一打開網頁就全部展開

created() {
    this.getExpends();
  },