An onerror handler that's a helluva lot more useful than `... catch(e) { alert(e) }`.You can easily hook this into a custom Google Analytics event to log your app's errors. Inspired by: http://bytes.com/topic/javascript/answers/90742-try-catch-error-handling-display-line-number

onerror.coffee

onerror = (err, file, line) ->
    logger """ # console.log, alert, whatever
        The following error occured: #{err}
        In file: #{file}
        At line: #{line}
    """

onerror.js

var onerror = function(err, file, line) {
    return alert("The following error occured: " + err + "\nIn file: " + file + "\nAt line: " + line);
};

Whoops - I didn't mean to publish this anonymously.

Forking for posterity. :)