IDBOpenDBRequest：blocked 事件

当对数据库的打开连接阻塞了同一数据库上的 versionchange 事务时，将执行 blocked 处理程序。

此事件不可取消，也不冒泡。

语法

在诸如 addEventListener() 的方法中使用事件名称，或设置事件处理程序属性。

addEventListener("blocked", (event) => {});

onblocked = (event) => {};

事件类型

一个 IDBVersionChangeEvent。继承自 Event。

事件属性

还继承了其父级 Event 接口的属性。

IDBVersionChangeEvent.oldVersion 只读: 返回数据库的旧版本。
IDBVersionChangeEvent.newVersion 只读: 返回数据库的新版本。

示例

使用 addEventListener()

// 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 属性

// 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");
  };
};

浏览器兼容性

BCD 表格仅在启用了 JavaScript 的浏览器中加载。

另请参阅

使用 IndexedDB