window.isCloseHint = true;
//初始化封闭
window.addEventListener("beforeunload", function(e) {
    if (window.isCloseHint) {
        var confirmationMessage = "要记得保留！你确定要脱离我吗？";
        (e || window.event).returnValue = confirmationMessage; // 兼容 Gecko + IE
        return confirmationMessage; // 兼容 Gecko + Webkit, Safari, Chrome
    }
});

假如你页面中有须要跳转而不像提醒对话框的处所（比方form表单提交），能够经由过程window.isCloseHint 变量来掌握。