Track mailto, file download and external links using Google Analytics

gistfile1.js

/*globals pageTracker: true */
(function () {
    "use strict";

    var delegate, clickCallback, handleLink, track;

    // generic delegate function
    delegate = function (element, tagName, eventName, callback) {
        var eventListener;

        tagName = tagName.toLowerCase();

        eventListener = function (event) {
            var target = event.target;

            while (target !== document.body && target !== element) {
                if (target.tagName && target.tagName.toLowerCase() === tagName) {
                    callback.call(target, event);
                    break;
                }
                target = target.parentNode;
            }
        };

        if ("function" === typeof element.addEventListener) {
            element.addEventListener(eventName, eventListener);
        } else if ("function" === typeof element.attachEvent) {
            element.attachEvent("on" + eventName, eventListener);
        }

    };

    track = function (page) {
        if ("object" === typeof(pageTracker) && "function" === typeof pageTracker._trackPageview) {
            pageTracker._trackPageview(page);
        }
    };

    handleLink = function (element) {
        var page;

        page = (element.pathname.charAt(0) === "/") ? element.pathname : "/" + element.pathname;

        if (element.search && element.pathname.indexOf(element.search) === -1) {
            page += element.search;
        }

        if (element.hostname !== location.host) {
            page = "/external/" + element.hostname + page;
        }

        track(page);
    };

    clickCallback = function (event) {
        var page, path, isDoc;
        if (this.protocol === "mailto:") {
            // handle mailto links
            page = "/mailto/" + this.href.substring(7);
            track(page);
        } else if (this.hostname === location.host) {
            // handle document downloads
            path = this.pathname + this.search;
            isDoc = path.match(/\.(?:doc|eps|jpg|png|svg|xls|ppt|pdf|xls|zip|txt|vsd|vxd|js|css|rar|exe|wma|mov|avi|wmv|mp3|docx|pptx|xlsx)($|\&|\?)/);
            if (isDoc) {
                handleLink(this);
            }
        } else if (!this.href.match(/^javascript:/)) {
            // handle external links
            handleLink(this);
        }
    };

    // use event delegation to track clicks.
    // this makes it possible to track links that are added with AJAX
    // and has a positive effect on performance, as there is only one eventhandler
    delegate(document.body, "a", "click", clickCallback);
}());