Chrome扩展程序-如何捕获所有运行时异常

Question

I'm working on a Chrome extension which has a background script (or event script ) which runs continuously and detects if certain web pages are visited in any tab and then does some processing.

I noticed that the script randomly stops working every now and then, but starts again if I restart the browser or inspect the console for the background script.

I know how to store data in chrome.storage.local and I want to be able to detect and make an entry everytime a runtime error is thrown, is this possible? ie a script wide catch block?

I saw this post which explains how to handle runtime errors, but this only works within a single callback function. I want to be able to do this for the whole script.

Answer 1

You are probably hitting the idle unload that Event pages use (since you say inspecting works - that wakes it up).

It was your choice to put in "persistent": false and it comes with consequences .

If you rely on any state variables, they will be lost when the page is unloaded. If you must keep any state at all, do it in chrome.storage.local .

Another common mistake is not re-registering all event listeners every time the script runs. The unload-but-remember-listeners mechanism depends on it; if an event is triggered, the following happens:

1. Check it there was any listener registered for the event. If not, do nothing.
2. If there was, the listener itself no longer exists (JS context is unloaded). Execute the page to reconstruct the context.
3. After the page stops executing (disregarding async code, Chrome won't wait), pick the listener registered in this run that matches the event and execute it.

So if you, say, registered a listener in a codepath that's not executed every time you run the script (eg not in a top-level statement but conditionally or asynchronously), then after waking up the script won't have that listener enabled and the event will be dropped:

/* Chrome wakes up your page */

chrome.storage.local.get("option", function(data) {
  if(data.option) {
    // Asynchronous
    chrome.someAPI.onSomeEvent.addListener(function() {
      // This will not be handled after unload
    });
  }
});

// Synchronous
chrome.someAPI.onSomeEvent.addListener(function() {
  // This will be handled after unload
  chrome.storage.local.get("option", function(data) {
    if(data.option) {
      // Do stuff
    });
  }
});

/* At this point, Chrome triggers the event,
   and if there are no listeners (re)registered it's lost */

So put any conditional/async processing inside the listeners.

There are also other reasons why it can stop working, but it's impossible to tell without seeing your code.