IDBRequest：error 事件
當某個錯誤導致請求失敗時，會執行 error 事件處理程式。在 error 事件處理程式中，你可以訪問請求的錯誤資訊，並向同一事務中放置更多請求。
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("error", (event) => { })
onerror = (event) => { }
事件型別
一個通用的 Event。
示例
此示例開啟一個數據庫並嘗試新增一條記錄，同時監聽 add() 操作的 error 事件（如果例如具有給定 taskTitle 的記錄已存在，則會發生此情況）
js
// Open the database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);
DBOpenRequest.addEventListener("upgradeneeded", (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.addEventListener("success", (event) => {
const db = DBOpenRequest.result;
// open a read/write db transaction, ready for adding the data
const transaction = db.transaction(["toDoList"], "readwrite");
const objectStore = transaction.objectStore("toDoList");
const newItem = {
taskTitle: "my task",
hours: 10,
minutes: 10,
day: 10,
month: "January",
year: 2020,
};
const objectStoreRequest = objectStore.add(newItem);
objectStoreRequest.addEventListener("error", () => {
console.log(`Error adding new item: ${newItem.taskTitle}`);
});
});
同一個示例，使用 onerror 屬性而不是 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) => {
const db = DBOpenRequest.result;
// open a read/write db transaction, ready for adding the data
const transaction = db.transaction(["toDoList"], "readwrite");
const objectStore = transaction.objectStore("toDoList");
const newItem = {
taskTitle: "my task",
hours: 10,
minutes: 10,
day: 10,
month: "January",
year: 2020,
};
const objectStoreRequest = objectStore.add(newItem);
objectStoreRequest.onerror = () => {
console.log(`Error adding new item: ${newItem.taskTitle}`);
};
};
規範
| 規範 |
|---|
| Indexed Database API 3.0 # eventdef-idbrequest-error |
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