js时钟显示

<script type="text/javascript">
	onload=function(){
		start();
		clock = window.setInterval('start()',1000);
		btn = document.getElementById('btn');
		btn.addEventListener('click',timeOut);
		btnTxt = btn.childNodes[0];
	}
	
	function start(){
		var date = new Date();
		
		var s = date.getSeconds();
		var i = date.getMinutes();
		var h = date.getHours();
		var d = date.getDate();
		var m = date.getMonth()+1;
		var y = date.getFullYear();

                //date.toLocaleDateString()——格式化本地日期
                //date.toLocaletimeString()——格式化本地时间

		var week = ['星期天','星期一','星期二','星期三','星期四','星期五','星期六'];
		week = week[date.getDay()];
		var str = y+'-'+m+'-'+d+'  '+h+':'+i+':'+s+'  '+week;
		
		var dv = document.getElementById('dv');
		var txt = document.createTextNode(str);
		dv.replaceChild(txt,dv.childNodes[0]);
	}
	
	function timeOut(){
		var start = document.createTextNode('开始');
		
		if(btn.firstChild.nodeValue=='暂停'){
			clearInterval(clock);
			var start = document.createTextNode('开始');
			btn.replaceChild(start,btn.childNodes[0]);
		}else if(btn.firstChild.nodeValue=='开始'){
			clock = window.setInterval('start()',1000);
			var start = document.createTextNode('暂停');
			btn.replaceChild(start,btn.childNodes[0]);
		}
	}
</script>

<div id="dv">这里显示时钟</div>
<button id="btn">暂停</button>