【Vue】绑定数据出错

<el-form-item label="订阅指标表是否显示索引号">
  <el-switch
    v-model="config.subscriptionsOption.defaultShowIndex"
    on-color="#13ce66"
    off-color="#ff4949">
    </el-switch>
 </el-form-item>
 
 <script>
 export default {
   data () {
     return {
       config: [
	   	  'subscriptionsOption': {
		  	"defaultShowDay": 10,
			"defaultShowIndex": true,
			"tableShowOption": {
			  "statisticsOption": [ ],
			  "moreOption": [ ],
			  "otherOption": [ ]
			}
		  }
	   ]
     }
   }
 }
 </script>

有观察到能正常改变配置值，但是这个显示 undefined 是怎么回事