使用 map 迭代對象數組時訪問數組內的嵌套對象值

Question

我的數組由多個對象組成，如下所示：

 {
        "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"
        }
    }

當我嘗試通過使用map遍歷數組來訪問嵌套對象產品中的值時，發生了一些奇怪的事情

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 */

當我嘗試訪問 produit 的屬性“nom_produit”的值時，出現此錯誤：

類型錯誤：無法讀取未定義的屬性“nom_produit”

盡管如此，我已經成功地記錄了嵌套對象產品！！

 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"
                             */

我真的找不到對這個奇怪結果的解釋。 如果 produit 對象已成功記錄，為什么在我嘗試訪問其屬性之一時將其視為未定義？

Answer 1

這絕對是荒謬的。 我添加了一個if else ，突然之間它起作用了：

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，如果我刪除該條件，我仍然會得到produit is undefined 錯誤，但條件檢查它不是未定義的並且它有效！

Answer 2

通過您顯示的日志：

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

我猜，你錯過了這個屬性的空間，試試

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

 const test = { "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", //You should check this attribute, is it " nom_produit" or "nom_produit" "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" } } console.log(test.produit[" nom_produit"]) console.log(test.produit["nom_produit"])