How to make javascript error console print out errors within callbacks?

Question

If I have a javascript error outside of a callback, Firebug console prints out the error. However, if I have ant error inside a callback, I will not see any printout.

document.observe('dom:loaded', function() {
    // not notified in console
    alert(undefinedVariable);
});

// notified in console
alert(anotherUndefinedVariable);

Almost all of my code is inside callbacks, so it is making it hard for me to track down errors. How do I print out every error in the console no matter where the error occurs?

Answer 1

I needed to tell Prototype to not swallow the exceptions.

Ajax.Responders.register({ 
        onException: function(request, exception) { 
                (function() { throw exception; }).defer(); 
        } 
});

Answer 2

您可以尝试显式打印到控制台-window.console.log（... something ...）应该可以在任何地方工作。