Firefox - show line number on "function not defined"?

Question

I need to track JS errors in browser, but when I run the function in FF I get 'function not defined' error. It does not give me a line number. It works in Chrome and maybe in IE too.

    window.onerror = function(errorMessage, url, line) {
  var loggerUrl = "https://www.xing.com/js/logger";
  var parameters = "?description=" + escape(errorMessage)
      + "&url=" + escape(url)
      + "&line=" + escape(line)
      + "&parent_url=" + escape(document.location.href)
      + "&user_agent=" + escape(navigator.userAgent);

  /** Send error to server */
  //new Image().src = loggerUrl + parameters;
  alert(loggerUrl + parameters);
};

HTML

<input type="button" onClick="test()" value="click">

Answer 1

There is a really good firefox addon "Firebug" which is exactely what you're looking for. Search Firebug in the Mozilla addon website.