更新版本时如何清除indexedDB中的所有数据？

Question

我有两个问题： 1. 我想在更新数据库版本时清除所有数据。

objectStore.clear();

但我有错误： main1.js:42 Uncaught ConstraintError: Failed to execute 'createObjectStore' on 'IDBDatabase': 具有指定名称的对象存储已经存在。

2. 当更新版本数据库只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("??? ??????? ?? ??????????? ?????????? ?????? IndexedDB. ?????-?? ??????? ????? ??????????");
   }
   var request = window.indexedDB.open("MyTestDatabase", 7);
   
   
   request.onupgradeneeded = function(e) {
   
       console.log( e.oldVersion )
   
       db = event.target.result;
       //console.log(db)
       // ??????? ????????? ???????? ??? ???? ???? ??????
      // 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) {
       // ??????? ???-?? ??? ?????? request.errorCode!
       console.log('error');
       console.log(event);
   };
   request.onsuccess = function(event) {
       // ????????? ?????-?? ??? ???? ?????? ???????? 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 将删除商店。

您收到错误，因为商店已经存在并且您正在尝试创建它。如果你想能够运行create，你必须deleteObjectStore首先。

但是，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。