Improving our javascript error reporting

Question

So right now we have some generic code to report errors either from our code or third party code. Our project is a JQM/Phonegap project for iOS. What is happening is we pretty much always get the same useless error... TypeError: 'undefined' is not a function... with no line number or other helpful information. Is there a way I could change the code to maybe get WHAT is undefined or WHERE it is?

window.onerror = function myErrorHandler(errorMsg, url, lineNumber) {
    //Handle errors not in a jquery event handler
    //DebugMessage(errorMSg + " "+ url + " " + lineNumber);
    var ex = new Error(errorMsg, url, lineNumber);
    HandleError(ex, "window.onerror");  
        //HandleError sends the error object to 
        //a webservice to log the error.
    return true;
};

Any tips on debugging javascript errors would help as well.

Answer 1

In recent months, browsers have extended the signature of window.onerror to provide more information.

window.onerror = function(msg, file, line, col, error) {

  // backwards compat
  if (!error) {
    error = new Error(msg);
  }

  // send error to your logger

}

This should give you a lot more information. But there are still things where you need better context. You should check out some third-party tools for this like TrackJS that automatically give you this, plus extra information on how the error occurred.

Disclaimer: I am one of the original authors of TrackJS, so I know a bunch about JavaScript errors :)