javascript - 如何从 Service Worker 发送 "offline"消息？

Question

我如何返回缓存，并显示一条消息说离线。可能吗？

到目前为止我的代码只是发回缓存:

const cachedFetch = request => request.method != 'GET' ? 

  fetch(request) : 
  caches.open("demo").then(cache =>
    cache.match(request).then(resp => {
      if(!!resp) {
        console.log('cache', request.url)
        return resp;// how to send custom message back with resp
      } else {
        console.log('not in cache', request.url)
        return fetch(request).then(response => {
         return response


        })
      }
    })
  )

self.addEventListener('fetch', event => event.respondWith(
    cachedFetch(event.request)
  )
)

Answer 1

Service Worker 可以使用 postMessage()通知客户。或者，应用程序也可以独立于 Service Worker 监听在线/离线事件:

https://developer.mozilla.org/en-US/docs/Web/API/NavigatorOnLine/Online_and_offline_events