IndexedDB 版本迁移与零停机升级

`title: IndexedDB 版本迁移与零停机升级``categories: Web 开发/前端/数据管理``keywords: IndexedDB,版本迁移,onupgradeneeded,零停机,兼容``description: 设计安全的 IndexedDB 版本迁移流程，采用幂等与向后兼容策略，实现零停机升级与平滑演进。`迁移策略幂等创建与更新对象仓库与索引，存在则跳过。小步快跑：多次小版本演进，避免大爆炸迁移。实现示例function openDB(name = 'app', version = 3) {

return new Promise((resolve, reject) => {

const req = indexedDB.open(name, version);

req.onupgradeneeded = () => {

const db = req.result;

if (!db.objectStoreNames.contains('items')) {

db.createObjectStore('items', { keyPath: 'id' });

}

const store = req.transaction.objectStore('items');

if (!store.indexNames.contains('byCreatedAt')) store.createIndex('byCreatedAt', 'createdAt');

if (!store.indexNames.contains('byOwner')) store.createIndex('byOwner', 'owner');

};

req.onsuccess = () => resolve(req.result);

req.onerror = () => reject(req.error);

});

}

版本变更处理监听 `onversionchange`，提示刷新或自动重连；迁移完成后恢复业务。