中没有特定事件Chrome扩展API 旨在用于此目的.

在">如何检测在线/离线事件跨浏览器? "，建议您使用 和事件(来自MDN ):

In "How to detect online/offline event cross-browser?" it is suggested that you can use window.navigator.onLine and the events (from MDN):

window.addEventListener('offline', function(e) { console.log('offline'); });
window.addEventListener('online', function(e) { console.log('online'); });

但是，我在Windows 10 x64上使用Chrome版本56.0.2924.87(64位)进行的测试表明，这些都不是有效的.当物理断开网络电缆的连接时，事件不会在后台脚本或内容脚本中触发.此外，两个脚本中的window.navigator.onLine值均保持为true.重新插入网络电缆时，同样也没有活动.

However, my testing on Windows 10 x64 using Chrome Version 56.0.2924.87 (64-bit) indicated that none of those are valid. When the network cable was physically disconnected, the events did not fire in either the background script, nor a content script In addition, the value of window.navigator.onLine remained true in both. There was a similar lack of activity when the network cable was plugged back in.

但是，当网络电缆断开连接时，会触发 webRequest .特别是以下事件:

However, when the network cable was disconnected a webRequest was fired. Specifically the following events:

webRequest.onBeforeRequest    ->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestId: "10787", tabId: -1, timeStamp: 1487550094371.293, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onBeforeSendHeaders->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestHeaders: Array[4], requestId: "10787", tabId: -1, timeStamp: 1487550094371.3901, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onSendHeaders      ->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestHeaders: Array[4], requestId: "10787", tabId: -1, timeStamp: 1487550094371.437, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onErrorOccurred    ->  arg[0]= Object { error: "net::ERR_NAME_NOT_RESOLVED", frameId: -1, fromCache: false, method: "GET", parentFrameId: -1, requestId: "10787", tabId: -1, timeStamp: 1487550096326.291, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }

重新连接电缆时，将触发以下webRequests序列:

When the cable was reconnected, the following sequence of webRequests were fired:

webRequest.onBeforeRequest    ->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestId: "10938", tabId: -1, timeStamp: 1487550516485.3562, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onBeforeSendHeaders->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestHeaders: Array[4], requestId: "10938", tabId: -1, timeStamp: 1487550516485.523, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onSendHeaders      ->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestHeaders: Array[4], requestId: "10938", tabId: -1, timeStamp: 1487550516485.565, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onHeadersReceived  ->  arg[0]= Object { frameId: -1, method: "GET", parentFrameId: -1, requestId: "10938", responseHeaders: Array[12], statusCode: 200, statusLine: "HTTP/1.1 200"tabId: -1, timeStamp: 1487550518279.5378, type: "other", url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onResponseStarted  ->  arg[0]= Object { frameId: -1, fromCache: false, ip: "216.58.193.68", method: "GET", parentFrameId: -1, requestId: "10938", responseHeaders: Array[12], statusCode: 200, statusLine: "HTTP/1.1 200", tabId: -1, timeStamp: 1487550518279.653type: "other"url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }
webRequest.onCompleted        ->  arg[0]= Object { frameId: -1, fromCache: false, ip: "216.58.193.68", method: "GET", parentFrameId: -1, requestId: "10938", responseHeaders: Array[12], statusCode: 200, statusLine: "HTTP/1.1 200", tabId: -1, timeStamp: 1487550518279.754type: "other"url: "https://www.google.com/searchdomaincheck?format=domain&type=chrome", __proto__: Object }

因此，看来要观看事件的***人选是 webRequest.onErrorOccurred 用于离线， webRequest.onCompleted 用于在线，两者都与网址:https://www.google.com/searchdomaincheck?format=domain&type=chrome.

So, it appears that good candidates for events to watch are webRequest.onErrorOccurred for going offline and webRequest.onCompleted for going online, both with the URL: https://www.google.com/searchdomaincheck?format=domain&type=chrome.

这将需要进一步测试.仅在上面提到的配置上进行过测试.

This would need further testing. It was only tested on the configuration mentioned above.