javascript - 服务 worker 中的全局错误处理是如何工作的？

Question

我找到了 https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerContainer/onerror其中说:

The onerror property of the ServiceWorkerContainer interface is an event handler fired whenever an error event occurs in the associated service workers.

但是我无法在 Chrome (v51) 中使用它。在主应用程序范围内，我从控制台运行了以下代码:

navigator.serviceWorker.onerror = function(e) { console.log('some identifiable string' + e); };

然后在active service worker的范围内我触发了一个任意错误:

f(); // f is undefined

结果是通常的“Uncaught ReferenceError: f is not defined(…)”错误消息，但它没有通过我的全局 onerror 处理程序记录。

MDN 页面说这个 API 自 v40 以来就在 Chrome 中得到支持，但是 navigator.serviceWorker.onerror 最初是未定义的，这让我相信它没有实现。有人熟悉这个吗？

Answer 1

也许您尝试像这样在 navigator.serviceWorker 容器上设置 onerror 处理程序:

// no effect outside service worker script
navigator.serviceWorker.onerror = function() {...};

必须使用 self.onerror 从 service worker 脚本中 设置错误处理程序(self 在这里是一个特殊的变量/属性指的是 ServiceWorkerGlobalScope )。 onerror 回调仅提供一条错误消息。

// inside service worker script
self.onerror = function(message) {
  console.log(message);
};

或者，您可以监听 service worker 的 error 事件，其中包含一个包含错误位置的 ErrorEvent:

// inside service worker script
self.addEventListener('error', function(e) {
  console.log(e.filename, e.lineno, e.colno, e.message);
});

这是一个 demo .请务必从 DevTools > Resources > Service Workers(在左侧面板) 中删除服务 worker ，因为它将填充这些失败的服务 worker 注册:

我已经验证了以下浏览器在 service worker 实例中支持 onerror:

• Chrome 51(稳定版)和 53(金丝雀版)
• 火狐 47
• Opera 38(稳定)和 39(开发者)

---

更新:

So when MDN describes the ServiceWorkerContainer interface, that is referring to self (ServiceWorkerGlobalScope) and not navigator.serviceWorker?

我认为这仅适用于 onerror 属性(可能也适用于那里的其他事件)，我猜规范尚未更新以反射(reflect)商定的实现。 ..

Service Workers 工作组已决定将 onerror 从 ServiceWorkerContainer 移到 Service Worker 实例中，如 GitHub ( slightlyoff/ServiceWorker #198 ) 中所述:

kinu commented on Apr 2, 2014

sgtm2. For error reporting (onerror stuff) we could probably do similar? E.g. moving .onerror handler from container to SW object, so that doc can explicitly know which SW the error is coming from (though it may need to attach handlers to multiple SWs).

然后在相关问题 (slightlyoff/ServiceWorker #104) 中有一个后续评论表明容器上的 onerror 缺乏用处:

jakearchibald commented on Apr 3, 2014

Thinking about the use-cases (following from #198)…

navigator.serviceWorker.onerror or navigator.serviceWorker.pending.onerror (whichever it becomes) are not useful for logging errors back to the server, as errors can happen outside of the life of any page. onerror inside the worker itself is best for that.

.pending.onerror is useful if you're updating the UI in response to an update. So maybe it's better as a statechange, although you'd need somewhere to put the error message.

That leaves errors that happen before the SW instance is created. AppCache has an error event that covers network-related update failures, and also parse failures. However, once again we'd lose any errors that happened outside the life of a page.