无法访问服务器时显示脱机缓存 [英] Show offline cache when server is unreachable

问题描述

当服务器关闭时，是否可以显示我网站的离线缓存？

Is it possible to show an offline cache of my website when the server is down?

我可以找到关于离线页面的所有示例都与客户端处于脱机状态有关。如果无法访问服务器，我需要向用户显示我的网站的缓存版本。

All the examples I can find regarding offline pages has to do with the client being offline. What I need is to show the user a cached version of my site if the server can't be reached.

我读过缓存清单，但它已被删除，导致许多问题。

I've read about the Cache Manifest in HMTL 5 but it's getting removed and it causes to many problems.

如果不使用任何其他负载均衡服务器，可以做些什么？

What can be done without using any other loadbalancing servers and such?

推荐答案

我最近了解到，使用Fetch API和服务工作者很简单：

I recently learned that with Fetch API and service workers its dead simple:

首先，注册服务工作者：

First, you register the Service worker:

  if (!navigator.serviceWorker) return;

  navigator.serviceWorker.register('/sw.js')

然后将其配置为缓存所需的内容：

Then configure it to cache whats needed:

self.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open(staticCacheName).then(function(cache) {
      return cache.addAll([
        '/',
        'js/main.js',
        'css/main.css',
        'imgs/icon.png',      
      ]);
    })
  );
});

如果电话没有响应，请使用Fetch API获取缓存的和平：

And use Fetch API to get cached peaces if no response from the call:

self.addEventListener('fetch', function(event) {
  event.respondWith(
    caches.match(event.request).then(function(response) {
      return response || fetch(event.request);
    })
  );
});

如果需要获得缓存版 如果服务器已关闭，请尝试喜欢：

if need to get cached version only if server is down, try something like:

self.addEventListener('fetch', function(event) {
  event.respondWith(
    return fetch(event.request).then(function(response) {
     if (response.status !== 200) {        
       caches.match(event.request).then(function(response) {
         return response;
       }).catch(function(error) {
         console.error('Fetching failed:', error);
         throw error;
      });
    })
  );
});

p.s。使用Fetch API似乎比实现旧的和令人讨厌的XMLHttpRequest更好。

p.s. using Fetch API seems much nicer way than implementing old and nasty XMLHttpRequest.

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