outbound link monitor for holmes

(function() {
    var MY_DOMAINS = ['image.baidu.com', 'tu.baidu.com'];

    var on = function(elem, event, handler) {
        if (elem.addEventListener) {
            elem.addEventListener(event, handler, false);
        } else if (elem.attachEvent) {
            elem.attachEvent('on' + event, handler);
        }
    };

    var getHost = function(url) {                                             
        var match = url.match(/^(https?:\/\/)?([^\/\?#]*)/);                        
        return match ? match[2].replace(/.*@/, '') : null;                          
    };

    var getAncestorByTag = function(element, tagName) {                   
        tagName = tagName.toUpperCase();                                        
        while ((element = element.parentNode) && element.nodeType == 1) {       
            if (element.tagName == tagName) {                                   
                return element;                                                 
            }                                                                   
        }                                                                       
        return null;                                                            
    };

    window._hmt = window._hmt || [];

    on(document, 'mousedown', function(e) {
        e = e || window.event;
        var target = e.target || e.srcElement;
        var a = (target.tagName == 'A' ? target : getAncestorByTag(target, 'a'));
        if (!a) { return; }
        var domain = getHost(a.href);
        for (var j = MY_DOMAINS.length - 1; j >= 0; j--) {
            var idx = domain.indexOf(MY_DOMAINS[j]);
            if (idx > -1 && idx + MY_DOMAINS[j].length == domain.length) { return; }
        }
        _hmt.push(['_trackEvent', 'OutboundLink', 'click', domain]);
    });
})();