checkNotification()
function checkNotification(){
	//判断是否支持Notification
	if(!("Notification" in window)){
		alert("浏览器不支持Notification,无法进行桌面提醒！");
	}
	//通知必须授权后才能显示，判断是否已授权
	//已授权情况
	else if(Notification.permission== "granted"){
		console.log("已授权")
		var notify= new Notification("李四",{body:"hello~",icon:‘img/aHead.png‘});
        var notifyST= setTimeout(function(){
        	notify.close();           
        	clearTimeout(notifyST);
        },2000)
	}
	//未授权且未拒绝
	else if(Notification.permission!= "denied"){
		//请求授权
		Notification.requestPermission(function(permission){
			//请求授权
			//授权成功
			if(permission== "granted"){
				console.log("请求授权成功！");
			}
		})
	}
};