//事件的封装
var EventUtil = {
addHandler: function (element, type, handler) {//注册事件
if (element.addEventListener) {//非IE
element.addEventListener(type, handler, false);
}
else if (element.attachEvent) {//IE
element.attachEvent("on" + type, handler);
}
else {//dom0级
element["on" + type] = handler;
}
},
removeHandler: function (element, type, handler) {//取消注册事件
if (element.removeEventListener) {//非IE
element.removeEventListener(type, handler, false);
}
else if (element.detachEvent) {//IE
element.detachEvent("on" + type, handler);
}
else {//dom0级
element["on" + type] = null;
}
},
getEvent: function (event) {//返回event的引用
return event ? event : window.event;
},
getTarget: function (event) {//返回鼠标单击的目标对象
return event.target || event.srcElement;
},
preventDefault: function (event) {//取消默认事件(a的href,radio,checkbox,)
if (event.preventDefault) {
event.preventDefault();
}
else {
event.returnValue = false;
}
},
stopPropagation: function (event) {//因为这个EventUtil只支持冒泡,不支持事件捕获,所以这个方法只能阻止冒泡
if (event.stopPrapagation) {
event.stopPropagation();
}
else {
event.cancelBubble = true;
}
},
getRelatedTarget: function (event) {//获取相关元素
/*
页面中有一个div;当鼠标离开这个div时,事件的主目标是div,而相关元素是body.
mouseover:事件的主目标是获得光标的元素,而相关元素就是那个失去光标的元素.
mouseout:事件的主目标是失去光标的元素,而相关元素使获得光标的那个元素.
*/
if (event.relatedTarget) { return event.relatedTarget; }
else if (event.toElement) { return event.toElement; }
else if (event.fromElement) { return event.fromElement; }
else { return null; }
},
getButton: function (event) {//获取鼠标按钮的点击方式
if (document.implementation.hasFeature("MouseEvents", "2.0")) { return event.button; }
else {
switch (event.button) {
case 0:
case 1:
case 3:
case 5:
case 7:
return 0; //左击
case 2:
case 6:
return 2; //中间键
case 4:
return 1; //右击
}
}
}
}; //是否在线的判断:
window.onload = function () {
function addMessage(str) {
var oDiv = document.getElementById("line");
var oP = document.createElement("p");
oP.innerHTML = str;
oDiv.appendChild(oP);
}
EventUtil.addHandler(window, "online", function () {
addMessage("在线");
});
EventUtil.addHandler(window, "offline", function () {
addMessage("不在线");
});
}
<body>
在线检测;
<div id="line"></div>
</body>
测试环境:
结果: