Implementation of HTML5 desktop notification prompt function

<button id="button">有人想加你为好友</button>
<p id="text"></p>
;(function (){
    if(window.Notification){
        var btn = document.getElementById("button");
        var txt = document.getElementById("text");
        btn.onclick = function (){
            if(Notification.permission == "granted"){
                popNotice();
            }else if(Notification.permission != "denied"){
                Notification.requestPermission().then(function (permission){
                    popNotice()
                })
            }
        };
        function popNotice(){
            if(Notification.permission == "granted"){
                var notification = new Notification("你好:",{
                    body:"请问今晚有空吗",
                    icon:"http://image.zhangxinxu.com/左边头像地址"
                });
                notification.onclick = function (){
                    txt.innerHTML = new Date().toTimeString().split(" ")[0]+"收到信息";
                    notification.close();
                }
            }
        }
    }else{
        console.log("浏览器不支持Notification");
    }
})();