}

    注意：像这样使用 update()和swapCache()并不会将更新后的资源 呈现给用户。这仅仅是让浏览器检查manifest文件是否发生了更新，然后下载指定的更新内容，重新填充app cache。因此，要让用户看到更新后的内容，需要两次页面下载，一次是更新app cache，一次是更新页面内容；

为了让用户能看到你的站点的最新版本，设置一个监听器来监听页面加载时的updateready 事件；

// Check if a new cache is available on page load.

　　window.addEventListener(‘load’, function(e) {

　　window.applicationCache.addEventListener(‘updateready’, function(e) {

　　if (window.applicationCache.status == window.applicationCache.UPDATEREADY) {

　　// Browser downloaded a new app cache.

　　// Swap it in and reload the page to get the new hotness.

　　window.applicationCache.swapCache();

　　if (confirm(‘A new version of this site is available. Load it?’)) {

　　window.location.reload();

　　}

　　} else {

　　// Manifest didn’t changed. Nothing new to server.

　　}

　　}, false);

　　}, false);

APPCACHE事件(APPCACHE EVENTS)

    有更多事件可以反映出cache的状态。在诸如下载、app cache更新、出现错误等事件都会让浏览器触发相应事件；
    下面的代码片段为每一类cache event都设置了监听器：

function handleCacheEvent(e) {

　　//…

　　}

　　function handleCacheError(e) {

　　alert(‘Error: Cache failed to update!’);

　　};

　　// Fired after the first cache of the manifest.

　　appCache.addEventListener(‘cached’, handleCacheEvent, false);

　　// Checking for an update. Always the first event fired in the sequence.

　　appCache.addEventListener(‘checking’, handleCacheEvent, false);

　　// An update was found. The browser is fetching resources.

　　appCache.addEventListener(‘downloading’, handleCacheEvent, false);

　　// The manifest returns 404 or 410, the download failed,

　　// or the manifest changed while the download was in progress.

　　appCache.addEventListener(‘error’, handleCacheError, false);

　　// Fired after the first download of the manifest.

　　appCache.addEventListener(‘noupdate’, handleCacheEvent, false);

　　// Fired if the manifest file returns a 404 or 410.

　　// This results in the application cache being deleted.

　　appCache.addEventListener(‘obsolete’, handleCacheEvent, false);

　　// Fired for each resource listed in the manifest as it is being fetched.

　　appCache.addEventListener(‘progress’, handleCacheEvent, false);

　　// Fired when the manifest resources have been newly redownloaded.