js获取时间戳，并同步显示当前时间

<p><span id="year">2020</span>年<span id="mouth">4</span>月<span id="day">22</span>日<span id="hour">15</span>时<span id="min">30</span>分<span id="secd">20</span>秒</p>
		
		<script type="text/javascript">
			var data = new Date();
			var year = data.getFullYear();
			var mouth = data.getMonth()+1;
			var day = data.getDay();//星期
			var dd = data.getDate();
			var hour = data.getHours();
			var min = data.getMinutes();
			var sec = data.getSeconds();
			timer()
			function timer(){
				setInterval(function(){
					if(sec<60){
						sec++
					}else{
						sec = 0; 
						if (min<60) {
							min++
						} else{
							min = 0;
							if (hour<24) {
								hour++
							} else{
								hour=0
							}
						}
					}
				    document.getElementById("secd").innerHTML = sec;	
				    document.getElementById("year").innerHTML = year;
					document.getElementById("mouth").innerHTML = mouth;
					document.getElementById("day").innerHTML = dd;
					document.getElementById("hour").innerHTML = hour;
					document.getElementById("min").innerHTML = min;
					document.getElementById("secd").innerHTML = sec;	
				},1000)
				
			}
			 
		</script>