js检测关闭页面或浏览器

window.addEventListener("beforeunload", function (e) {
var confirmationMessage = "\o/";
(e || window.event).returnValue = confirmationMessage; //Gecko + IE
return confirmationMessage;                            //Webkit, Safari, Chrome
});

window.onbeforeunload = function () {
return "Do you really want to close?";
};