Chrome Extensions: Background Script Catch Network and HTTP Errors

Question

I\'m developing a small Chrome extension for personal use on a very specific case (website automation) but I\'ve a problem. How can I catch a network error on a background s

Answer 1

I assume that from the perspective of webRequest / Chrome's network stack, this request actually completed. So you need to hook to some other event, e.g.

function extractStatus(line) {
  var match = line.match(/[^ ]* (\d{3}) (.*)/);
  if(match) {
    return {code: match[1], message: match[2]};
  } else {
    return undefined;
  }
}

chrome.webRequest.onHeadersReceived.addListener(
  function(details) {
    var status = extractStatus(details.statusLine);
    if(status) {
      // Do something based on status.code
    }
  },
  {urls: [""]}
);

Note that this event is optionally blocking: you can redirect the request if needed.

Obviously, this will create a lot of work for your extension; in the above snippet, the listener is not blocking, but if you do make it blocking it will slow down your Chrome considerably - only use it when absolutely necessary and filter by URL when appropriate.