IDBOpenDBRequest: blocked 事件
當一個開啟的資料庫連線阻止了同一資料庫上的 versionchange 事務時，會執行 blocked 處理程式。
此事件不可取消，也不會冒泡。
語法
在諸如 addEventListener() 之類的方法中使用事件名稱，或設定事件處理程式屬性。
js
addEventListener("blocked", (event) => { })
onblocked = (event) => { }
事件型別
一個 IDBVersionChangeEvent。繼承自 Event。
事件屬性
也繼承自其父介面 Event 的屬性。
IDBVersionChangeEvent.oldVersion只讀-
返回資料庫的舊版本。
IDBVersionChangeEvent.newVersion只讀-
返回資料庫的新版本。
示例
使用 addEventListener()
js
// Open the database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);
DBOpenRequest.onupgradeneeded = (event) => {
const db = event.target.result;
db.onerror = () => {
console.log("Error creating database");
};
// Create an objectStore for this database
const objectStore = db.createObjectStore("toDoList", {
keyPath: "taskTitle",
});
// define what data items the objectStore will contain
objectStore.createIndex("hours", "hours", { unique: false });
objectStore.createIndex("minutes", "minutes", { unique: false });
objectStore.createIndex("day", "day", { unique: false });
objectStore.createIndex("month", "month", { unique: false });
objectStore.createIndex("year", "year", { unique: false });
};
DBOpenRequest.onsuccess = (event) => {
// Let's try to open the same database with a higher revision version
const req2 = indexedDB.open("toDoList", 5);
// In this case the onblocked handler will be executed
req2.addEventListener("blocked", () => {
console.log("Request was blocked");
});
};
使用 onblocked 屬性
js
// Open the database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);
DBOpenRequest.onupgradeneeded = (event) => {
const db = event.target.result;
db.onerror = () => {
console.log("Error creating database");
};
// Create an objectStore for this database
const objectStore = db.createObjectStore("toDoList", {
keyPath: "taskTitle",
});
// define what data items the objectStore will contain
objectStore.createIndex("hours", "hours", { unique: false });
objectStore.createIndex("minutes", "minutes", { unique: false });
objectStore.createIndex("day", "day", { unique: false });
objectStore.createIndex("month", "month", { unique: false });
objectStore.createIndex("year", "year", { unique: false });
};
DBOpenRequest.onsuccess = (event) => {
// Let's try to open the same database with a higher revision version
const req2 = indexedDB.open("toDoList", 5);
// In this case the onblocked handler will be executed
req2.onblocked = () => {
console.log("Request was blocked");
};
};
規範
| 規範 |
|---|
| Indexed Database API 3.0 # eventdef-idbopendbrequest-blocked |
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