Util object with Generic Handling of ajax errors when using jquery and spinner on off

util-jquery-global-ajax-handler-and-spinner.js

/*
util object; setSpinnerNextTo, setSpinnerOff; globalAjaxErrorHandler

assumes you have a property on your namespace of env, most likely set via server side code
YOUR_NAMESPACE.env = "DEVELOPMENT"; // STAGING, PRODUCTION
YOUR_NAMESPACE.env = '<%= Rails.env.upcase %>'; // rails 
YOUR_NAMESPACE.env = '<%= ApplicationState %>'; // asp, assuming you have an ApplicationState property :)

initialize the global error handling - http://api.jquery.com/ajaxError
jQuery(document).ajaxError(YOUR_NAMESPACE.util.globalAjaxErrorHandler);

right now it is set to parse on asp.net html errors, modify as needed for you needs 
*/
var undef; // undefined
var YOUR_NAMESPACE = YOUR_NAMESPACE || {};
YOUR_NAMESPACE.util = {
    // ************************************************************
    setSpinnerNextTo: function (controlID, topOffset, leftOffset) {
        // log(controlID);
        if (controlID !== undef && controlID !== null && controlID !== "") {
            if (topOffset === undef || topOffset === null) {
                topOffset = 0;
            }
            if (leftOffset === undef || leftOffset === null) {
                leftOffset = 14;
            }
            var $control = jQuery(controlID);
            if ($control.length === 0) {
                return;
            }

            var offset = $control.offset();
            var top = offset.top + topOffset;
            var left = offset.left + leftOffset + $control.width();

            // sometimes things are not what they seem, use the parent coordinates if needed
            if (left < 0) {
                left = jQuery(controlID).parent().offset().left + leftOffset;
            }

            // show it
            jQuery('#spinner').css('top', top).css('left', left).show().css('z-index', 33010);
        }
    },

    // ************************************************************
    setSpinnerOff: function () {
        jQuery('#spinner').hide();
    },

    // ************************************************************
    globalAjaxErrorHandler: function (e, xhr, settings, exception) {
        var ct;
        var fragment;
        var lengthOfVisibleErrorMessage = 0;
        var baseMessage = "Error: ";
        var exceptionMessage = exception ? exception.message : xhr.responseText;
        // display one of these
        var friendly = baseMessage;
        var local = baseMessage + xhr.status + ", " + xhr.statusText + "\n" + settings.url + "\n";

        if (xhr.status === 404) {
            friendly = friendly + "Page not found";
        }
        else {
            friendly = friendly + " an exception has occurred\nPlease try again";
        }

        if (YOUR_NAMESPACE) {
            YOUR_NAMESPACE.util.setSpinnerOff();

            if (YOUR_NAMESPACE.env === "DEVELOPMENT") {
                ct = xhr.getResponseHeader("content-type") || "";
                if (ct.indexOf('html') > -1) {
                    // parse our error message a bit, try to make it easier on devs
                    // based on the way asp generates html errors
                    fragment = $(exceptionMessage).find("h2");
                    local = local + "\n" + fragment.text();
                    fragment = $(exceptionMessage).find("pre");

                    if (fragment.length > 0) {
                        fragment.each(function () {
                            local = local + "\n" + $(this).text();
                        });
                    }
                }
                else {
                    // json, text, xml, etc... add specific parsing later if needed
                    local = local + "\n" + exceptionMessage;
                }

                lengthOfVisibleErrorMessage = (local.length > 350) ? 350 : local.length;
                alert(local.substring(0, lengthOfVisibleErrorMessage) + "...\n\n  - Check firebug console for more info.\n  - This message for development only.");
            }
            else {
                alert(friendly);
            }
        }
        else {
            // log("FATAL: YOUR_NAMESPACE instance not found.");
            alert(friendly);
        }
    }
};