Automatically report unhandled javascript exceptions to your server!

reporter.js

(function(exports) {
    function nop() {}

    // IE doesn't always have console, place a no-op shim for it.
    if (!window.console) {
        window.console = {log: nop, info: nop, warn: nop, error: nop};
    }

    // Transforms an Error to a simple object that can be JSONified.
    function error_to_object(error) {
        var newError = {message: error.message, url: error.fileName, lineNumber: error.lineNumber};
        if (error.constructor && error.constructor.name)
            newError.type = error.constructor.name;
        // get anything missed. For some reason error.message doesn't show up in this pass.
        for (var prop in error) {
            if (!error.hasOwnProperty(prop)) continue;
            var newProp;
            if (prop == "fileName")
                newProp = "url";
            else
                newProp = prop;
            newError[newProp] = error[prop];
        }
        return newError;
    }
    exports.error_to_object = error_to_object;

    var max_retry_time = 5*60*1000;
    var logger_url = '/logger.php';

    var no_send_before = 0;
    var no_send_delay = 10;
    var send_queued = 0;
    var send_max_queued = 7;

    function send_error(error, retry_time) {
        if (typeof error === "string")
            error = {message: error};
        else if (error instanceof Error)
            error = error_to_object(error);

        if (!error.hasOwnProperty("message")) {
            console.error("send_error called without error.message", error);
            return;
        }

        error.pageurl = document.location.href;
        var errorString = JSON.stringify(error);

        var now = (new Date()).getTime();
        if (now < no_send_before) {
            if (send_queued < send_max_queued) {
                send_queued++;
                setTimeout(function() {
                    send_queued--;
                    send_error(error, retry_time);
                }, no_send_before-now+10);
            }
            return;
        }

        if (!retry_time)
            retry_time = 3*1000;
        else if (retry_time > max_retry_time)
            retry_time = max_retry_time;

        no_send_before = now + no_send_delay;

        no_send_delay *= 2;
        if (no_send_delay > max_retry_time)
            no_send_delay = max_retry_time;

        $.ajax({
            url: logger_url,
            cache: false,
            data: {type: "error", data: errorString},
            type: 'POST',
            success: function(data) {
                console.log("sent javascript error report to server for review");
            },
            error: function(jqXHR, textStatus, errorThrown) {
                if (textStatus == "timeout") {
                    console.log("timeout while trying to send error report, retrying soon");
                    setTimeout(function() {
                        send_error(error, retry_time*2);
                    }, retry_time);
                } else {
                    console.error("could not send error report. textStatus: "+textStatus+", errorThrown: "+errorThrown);
                }
            }
        });
    }
    exports.send_error = send_error;

    var old_onerror = window.onerror;

    window.onerror = function(errorMsg, url, lineNumber, column, errorObj) {
        try {
            if (errorObj !== undefined) {
                send_error(errorObj);
            } else {
                var error = {message: errorMsg, url: url, lineNumber: lineNumber, column: column, caughtBy: "window.onerror"};
                send_error(error);
            }

            if (old_onerror)
                old_onerror.apply(this, arguments);
        } catch(e) {
            // Important. If we have an error in the automatic error reporter,
            // we need to make sure we don't get in an infinite loop of trying
            // to report it, triggering it again, and trying to report it again.
            try {
                send_error(e);
            } catch(e) {}
        }
        return false;
    };
})(window.reporter||(window.reporter={}));

Hi,
I tried your script. The idea is great, but unfortunately the script itself raises some errors:

{"message":"Converting circular structure to JSON","type":"circular_structure","stack":"TypeError: Converting circular structure to JSON\n at Object.stringify (native)\n at send_error (.../reporter.js:11:59)\n
User-Agent: Mozilla/5.0 (Linux; U; Android 2.3.6; es-es; GT-I9070 Build/GINGERBREAD) App
leWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1

{"message":"Cannot call method 'hasOwnProperty' of null","type":"TypeError", ... }
User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36