无法将元素推送到数组

Question

我试图将元素推送到数组的末尾，名为＆＃34; toServiceSubCatNamesList＆＃34;

this.toServiceSubCatNamesList.push(this.loadServiceTypes.serviceTypes[j]);

＆＃34; loadServiceTypes＆＃34;的结构数组是：

{
"serviceTypes": [
    {
        "service_type_id": 1,
        "service_type_name": "Cutting",
        "service_type_price": "3000.00",
        "created_at": null,
        "updated_at": null,
        "pivot": {
            "service_service_type_service_id": 1,
            "service_service_type_service_type_id": 1
        }
    }
  ]
}

＆＃34; toServiceSubCatNamesList＆＃34;的结构数组是：

toServiceSubCatNamesList > 0:Object
                                 created_at:null
                                 pivot:Object
                                 service_type_id:1
                                 service_type_name:"Washing"
                                 service_type_price:"3000.00"
                                 updated_at:null
                                 __proto__:Object
                                 length:1
                                 __proto__:Array(0)

当我这样做时，它会给出错误＆＃34; TypeError：无法读取属性＆＃39; service_type_name＆＃39;未定义＆＃34;。有任何建议可以克服这个问题！