IDBDatabase: versionchange 事件
当在其他地方（很可能是在同一台计算机上的另一个窗口/标签页中）请求更改数据库结构（在 IDBOpenDBRequest 上发送 upgradeneeded 事件或调用 IDBFactory.deleteDatabase）时，会触发 versionchange 事件。
语法
在诸如 addEventListener() 之类的方法中使用事件名称，或设置事件处理程序属性。
js
addEventListener("versionchange", (event) => { })
onversionchange = (event) => { }
事件类型
一个通用的 Event。
示例
此示例打开一个数据库，成功后添加一个 versionchange 监听器
js
// Open the database
const dBOpenRequest = window.indexedDB.open("Nonexistent", 4);
dBOpenRequest.onupgradeneeded = (event) => {
const db = event.target.result;
// 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 = event.target.result;
db.addEventListener("versionchange", (event) => {
console.log("The version of this database has changed");
});
});
同一示例，使用 onversionchange 事件处理程序属性
js
// Open the database
const dBOpenRequest = window.indexedDB.open("Nonexistent", 4);
dBOpenRequest.onupgradeneeded = (event) => {
const db = event.target.result;
// 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 = event.target.result;
db.onversionchange = (event) => {
console.log("The version of this database has changed");
};
};
规范
| 规范 |
|---|
| Indexed Database API 3.0 # eventdef-idbdatabase-versionchange |
| Indexed Database API 3.0 # dom-idbdatabase-onversionchange |
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