CODEWITHSUNDEEP
javascriptgoogle-chromegoogle-chrome-extension
huczilla
huczilla

Reputation: 973

Chrome extension: how to trap/handle content-script errors globally?

In a Chrome extension, is there a way to globally trap/handle Javascript errors occurring in a content-script? (e.g. for submission to a Javascript error tracking service like bugsnag)

Ideally, I would setup a global window.onerror handler at the top of the content script. But it's not working properly in Chrome 40: the error is caught, but the information supplied is useless: a message of 'Script error' and no url, lineNumber, column or error object with stack.

I created a test extension to show this busted behaviour for content scripts. Details below. Interesting findings:

Reproducing busted window.onerror for Chrome extension content script.

In a new folder, create manifest.json, content-script.js and background-script.js. Then load into Chrome via Window > Extensions > Load unpacked Extension.

manifest.json

{
    "name": "Chrome extension content-script errors test",
    "manifest_version": 2,
    "version": "0.0.1",
    "background": {
      "scripts": [ "background-script.js" ]
    },
    "content_scripts": [{
        "matches": ["<all_urls>"],
        "js": ["content-script.js"]
    }]
}

content-script.js

window.onerror = function (errorMsg, url, lineNumber, column, errorObj) {
    console.log('Caught content script error');
    console.log('errorMsg: ' + errorMsg);
    console.log('url: ' + url);
    console.log('lineNumber: ' + lineNumber);
    console.log('column: ' + column);
    console.log('errorObj follows:');
    console.log(errorObj);
    return true;
};

console.log('I am a content script, about to throw an error');
throw new Error('Is this error caught?');

background-script.js

window.onerror = function (errorMsg, url, lineNumber, column, errorObj) {
    console.log('Caught background script error');
    console.log('errorMsg: ' + errorMsg);
    console.log('url: ' + url);
    console.log('lineNumber: ' + column);
    console.log('column: ' + column);
    console.log('errorObj follows:');
    console.log(errorObj);
    return true;
};

//To see nice window.onerror behaviour for background script..
//Uncomment 2 lines below, reload extension, and look at extension console
//console.log('I am a background script, about to throw an error');
//throw new Error('Is this error caught?');

Upvotes: 46

Views: 13616

Answers (3)

barbushin
barbushin

Reputation: 5305

See the most complete errors handling by Chrome extension content script in https://github.com/barbushin/javascript-errors-notifier/blob/master/content.js - it's source code of JavaScript Errors Notifier extension.

Upvotes: 0

huczilla
huczilla

Reputation: 973

5 months after asking this question, I'm now pretty convinced there isn't currently an easy way to global trap/handle Javascript errors occurring in a content script. As such,

  • I've created a Chrome bug report: window.onerror should contain useful info for thrown error in extension content script. Feel free to chip in with useful comments.
  • If you need to globally trap content script errors, your best bet is to assume window.onerror is busted for now in content scripts. Instead, wrap all Javascript code in try-catch blocks, which gives you access to useful error information. This is trickier than it sounds, as you have to handle both synchronous code (easy) and asynchronous-callback code (trickier). Take a look at this article for starters, and good luck!

Upvotes: 35

Wim Mostmans
Wim Mostmans

Reputation: 3601

Check out TraceKit, that's what we use at our company to do all front-end error logging. If you combine it with a javascript client library for your favorite logging service you're all set.

Upvotes: -1

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