javascript - 版本更新时如何清除indexedDB中的所有数据？

Question

我有两个问题:1.我希望当我更新数据库版本时清除所有数据。

objectStore.clear();

但我有错误:ma​​in1.js:42 Uncaught ConstraintError: 无法在“IDBDatabase”上执行“createObjectStore”:指定名称的对象存储已存在。

更新版本数据库仅向我的数据库添加新项目时如何？

var browserDatabase={};

browserDatabase._db = null;
browserDatabase._dbVersion = 4;
browserDatabase._dbName = "mediaStorageDB";
browserDatabase._storeName = "myStore";
var idb = window.indexedDB

var IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction;
var IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange;

var dbName='nameDb';

if (!window.indexedDB) {
   // window.alert("Ваш браузер не поддерживат стабильную версию IndexedDB. Такие-то функции будут недоступны");
}
var request = window.indexedDB.open("MyTestDatabase", 7);


request.onupgradeneeded = function(e) {

    console.log( e.oldVersion )

    db = event.target.result;
    //console.log(db)
    // Создаем хранилище объектов для этой базы данных
   // var objectStore = db.createObjectStore("name", { keyPath: "myKey" })
    const customerData = [
        { ssn: "444-44-4444", name: "Bill", age: 35, email: "bill@company.com" },
        { ssn: "555-55-5555", name: "Donna", age: 32, email: "donna@home.org" }
    ];



    var objectStore = db.createObjectStore("customers", { keyPath: "ssn" });

    // Create an index to search customers by name. We may have duplicates
    // so we can't use a unique index.
    objectStore.createIndex("name", "name", { unique: false });

    // Create an index to search customers by email. We want to ensure that
    // no two customers have the same email, so use a unique index.
    objectStore.createIndex("email", "email", { unique: true });


    objectStore.clear(); //clear previous version



    // Store values in the newly created objectStore.
    for (var i in customerData) {
        objectStore.add(customerData[i]);
    }

    if (e.oldVersion < 1) {
        // create v1 schema
    }
    if (e.oldVersion < 2) {
        // upgrade v1 to v2 schema
    }
    if (e.oldVersion < 3) {
        // upgrade v2 to v3 schema
    }
    // ...
};
request.onerror = function(event) {
    // Сделать что-то при ошибке request.errorCode!
    console.log('error');
    console.log(event);
};
request.onsuccess = function(event) {
    // Выполнить какой-то код если запрос успешный request.result!
    console.log('success');

    db = event.target.result;
    console.log(db);

    var transaction = db.transaction(["customers"], "readwrite");


    const customerData = [
        { ssn: "888-44-4444", name: "Sasga", age: 35, email: "sasha@company.com" },
        { ssn: "99-55-5555", name: "Andrii", age: 32, email: "andrii@home.org" }
    ];
    var objectStore = transaction.objectStore("customers");
    for (var i in customerData) {
        var request = objectStore.add(customerData[i]);
        request.onsuccess = function(event) {
            // event.target.result == customerData[i].ssn;
        };
    }


    transaction.oncomplete = function(event) {
        console.log("All done!");
    };

    transaction.onerror = function(event) {
        // Don't forget to handle errors!
    };


};

Answer 1

clear 将删除存储中的所有数据。

deleteObjectStore 将删除存储。

您收到错误是因为商店已存在并且您正在尝试创建它。如果您希望能够运行create，则必须先deleteObjectStore。

然而，这可能不是您最终想要做的。在版本更改中，您通常不想删除对象存储、索引和数据。您只想更新它们。