Service Worker 缓存层级回退与优先级调度

`title: Service Worker 缓存层级回退与优先级调度``categories: Web 开发/前端/数据管理``keywords: Service Worker,缓存层级,回退,优先级,调度``description: 设计静态/动态/预取三层缓存与优先级调度策略，在失败时逐级回退并记录命中，提升稳定性与可观测性。`策略静态层（版本化）优先，动态层（短期）次之，预取层（候选）最后；记录命中来源。代码片段self.addEventListener('fetch', (event) => {

event.respondWith((async () => {

const req = event.request;

const staticC = await caches.open('static-v2');

const dynC = await caches.open('dynamic');

const preC = await caches.open('prefetch');

return (await staticC.match(req)) || (await dynC.match(req)) || (await preC.match(req)) || fetch(req);

})());

});