The State of Client side JavaScript Error Reporting

    window.onerror = function(msg,url,line,col,err) { 
      console.log(err.stack) 
    }

    window.onerror = function() {
      console.log(window.event.error.stack)
    }

    throw JSON.stringify(some_var_to_watch);

Another option could be to disable all inline scripts via CSP, which will hit the older generation of Chrome extensions (and I think the newer ones doesn't trigger onerror).

Here is a sample of a few we regularly get:

* Out of stack space

* TypeError: Unable to delete property.

* [object Event]

* Error​ load​ing s​cript

* Synta​x err​or

    window.onerror = function( error, url, lineno ){
      if ( url && url.match( //https?:\/\/.*?assets/ ) ){
        # error management
      }
    }

Of course if you inline js for performance on production code, that's a problem.

EDIT : an other important thing to avoid flooding is to handle amount of error. Javascript errors rarely come alone. An error within an event callback may be triggered several times before user surrenders. And let not even start with error within setInterval. To avoid this, I usually use a `error_got` counter and simply silence error reporting for the current page / context when I've got more than 5 errors.

And about user surrendering. Reporting errors is nice. Preventing user to get stuck is better. I always automatically disable all callbacks in onerror and let default html actions on links and form being process. This ensure user intent will be fulfilled and page context will be reloaded as a bonus. I've written more extensively on this here : https://gist.github.com/oelmekki/6420982