下拉框change事件取key和value值

<el-col :span="20">
            <el-form-item label="班组" prop="groupCode">
              <el-select v-model="form.groupCode" value-key="value" placeholder="请选择班组" @change="groupChanged"   
    size="small">
                <el-option v-for="item in groupType" :key="item.groupCode" :label="item.groupName" :value="item.groupCode">
                </el-option>
              </el-select>
              <el-input v-model="form.groupName" v-show="false"></el-input>
            </el-form-item>
</el-col>

    groupChanged(e) {
      let obj = {};
      obj = this.groupType.find(item => {
        return item.groupCode === e;
      });
      this.form.groupName = obj.groupName;
    },