javascript检测网络是否畅通、具体连接功能的代码

var EventUtil = {
addHandler: function (element, type, handler) {
if (element.addEventListener) {
element.addEventListener(type, handler, false);
} else if (element.attachEvent) {
element.attachEvent("on" + type, handler);
} else {
element["on" + type] = handler;
}
},
removeHandler: function (element, type, handler) {
if (element.removeEventListener) {
element.removeEventListener(type, handler, false);
} else if (element.detachEvent) {
element.detachEvent("on" + type, handler);
} else {
element["on" + type] = null;
}
}
};

var dom = document.createElement('img');
dom.style = 'display:none;';
dom.src = 'http: //www.baidu.com/img/bdlogo.gif';
dom.id = 'map_img';
EventUtil.addHandler(dom, 'error', function(){

alert('你的电脑没有链接网络，连接上网络后才能打开地图！');
});
document.body.appendChild(dom);