Question

我的数组由如下多个对象组成：

 {
        "id": 2,
        "nom_operation": "opSavCreationTest2",
        "num_serie": "1203250cd81b2101",
        "address_mac": "04:15:d9:00:00:49",
        "description": "opSavCreationTest2",
        "adminId": 82,
        "produitId": 1,
        "clientId": 2,
        "status": "produit_recu",
        "lieu_achat_produit": "opSavCreationTest2",
        "garanti_au": "07-02-2021",
        "createdAt": "2020-03-27T15:15:55.207Z",
        "updatedAt": "2020-03-27T15:15:55.207Z",
        "produit": {
            "id": 1,
            "nom_produit": "PURE BLACK MAT",
            "type_produit": "Pure",
            "couleur_produit": "black_mat",
            "nbr_op_sav_en_cours": 7,
            "img": "img",
            "createdAt": "2020-03-30T08:41:39.597Z",
            "updatedAt": "2020-03-30T15:37:09.294Z"
        },
        "client": {
            "id": 2,
            "nomClient": "opSavCreationTest2",
            "numTel": "5775757575",
            "email": "opSavCreationTest2",
            "addresse": "opSavCreationTest2",
            "ville": "opSavCreationTest2",
            "pays": "opSavCreationTest2",
            "createdAt": "2020-03-27T15:15:55.043Z",
            "updatedAt": "2020-03-27T15:15:55.043Z"
        },
        "admin": {
            "id": 82,
            "nom": "administrateur",
            "email": "aeaffeef@gmail.com",
            "mot_de_passe": "efefr3lnr8Fr4IwEsc=",
            "last_login": null,
            "role": "administrateur",
            "createdAt": "2020-03-23T09:08:43.585Z",
            "updatedAt": "2020-03-23T09:08:43.585Z"
        }
    }

当我尝试通过使用map遍历数组来访问嵌套对象产品中的值时，会发生奇怪的事情

this.state.operationSavInformation.map(
                      (operationSavInformation, i) => {
                        const operationSavLink = `/home/operationSav/${operationSavInformation.id}`;
                        console.log("operationSavInformation ", i);
                        console.log("operationSavInformation.produit"); // Works
                        console.log(operationSavInformation.produit);
                        /** LOGS THIS:
                         *
                         * id: 1
                         *  nom_produit: "PURE BLACK MAT"
                         * type_produit: "Pure"
                         * couleur_produit: "black_mat"
                         * nbr_op_sav_en_cours: 7
                         * img: "img"
                         * createdAt: "2020-03-30T08:41:39.597Z"
                         * updatedAt: "2020-03-30T15:37:09.294Z"
                         */

                        console.log(
                          operationSavInformation.produit["nom_produit"]
                        ); //ERROR

                        /**TypeError: Cannot read property 'nom_produit' of undefined */

当我尝试访问产品的属性'nom_produit'的值时，出现此错误：

TypeError：无法读取未定义的属性'nom_produit'

尽管如此，我已经成功记录了嵌套对象产品！

 console.log("operationSavInformation.produit"); // Works
                            console.log(operationSavInformation.produit);
                            /** LOGS THIS:
                             *
                             * id: 1
                             *  nom_produit: "PURE BLACK MAT"
                             * type_produit: "Pure"
                             * couleur_produit: "black_mat"
                             * nbr_op_sav_en_cours: 7
                             * img: "img"
                             * createdAt: "2020-03-30T08:41:39.597Z"
                             * updatedAt: "2020-03-30T15:37:09.294Z"
                             */

我真的找不到这种奇怪结果的解释。如果成功记录了产品对象，为什么在我尝试访问其属性之一时将其视为未定义？

Answer 1

这绝对是荒谬的。我添加了if else，突然之间一切正常：

this.state.operationSavInformation.map(
            (operationSavInformation, i) => {
                const operationSavLink = `/home/operationSav/${operationSavInformation.id}`;
                console.log("operationSavInformation ", i);
                console.log("operationSavInformation.produit"); // Works
                console.log(operationSavInformation.produit);
                const produit = operationSavInformation.produit;
                console.log(
                  "produit = operationSavInformation.produit;"
                );
                console.log(produit);
                if (produit !== undefined) {
                  // This gets executed despite the error without if else says that produit is undefined!!
                  console.log("produit is not undefined");
                  console.log(produit.nom_produit);
                } else {
                  // This doesn't get executed despite the error without the if else is that it cannot read nom_produit of undefined
                  console.log("produit is undefined");
                }}

但是，如果我删除该条件，我仍然会收到产品未定义错误，但是条件会检查它是否未定义并且可以工作！

Answer 2

通过显示的日志：

this.filteredOptions =  this.userService
  .getUserSuggestions(this.displayName, 30)
  .pipe(
    map(response => someVariable ? response.filter(option => option.eMail != null) : response),
    debounceTime(400),
    distinctUntilChanged()
  );

我想，您可能会错过此属性的空格，请尝试

** LOGS THIS: * * id: 1 * nom_produit: "PURE BLACK MAT" // " nom_produit" should be right * type_produit: "Pure"

console.log(operationSavInformation.produit[" nom_produit"])

使用map迭代对象数组时，访问数组内的嵌套对象值

2 个答案: