怎样知道今天是今年的第几周呢？用javascript代码实现

Question

var today =new Date();
  var beginDay=new Date(today.getFullYear(),0,0)
  var weekNo=parseInt((today.getTime()-beginDay.getTime())/(7*60*60*24*1000))
  alert("这是本年的第"+weekNo+"周！")

Answer 1

<script language="JavaScript">
<!--
var dt0=new Date();
var dt1=new Date(dt0.getFullYear(),1,1);
var m=(dt0.valueOf()-dt1.valueOf())/1000/60/60/24/7+0.5;
var n=parseInt(m);
if(n<m) n++;
alert('现在是本年度第'+n.toString()+'周');
-->
</script>

Answer 2

经测试^_^...
 shyslysky(飞天) ( ) 信誉：100
误差小一点..
最后再把周+1即可
完整如下:
<script>
var today =new Date();
var beginDay=new Date(today.getFullYear(),0,0)
var weekNo=parseInt((today.getTime()-beginDay.getTime())/(7*60*60*24*1000))
alert("这是本年的第"+eval(weekNo+1)+"周！")
</script>

Answer 3

或:
eglic(圪圪) ( ) 信誉：97 <script language="JavaScript">
<!--
var dt0=new Date();
var dt1=new Date(dt0.getFullYear(),0,0);
var m=(dt0.valueOf()-dt1.valueOf())/1000/60/60/24/7+0.5;
var n=parseInt(m);
if(n<m) n++;
alert('现在是本年度第'+(n.toString()-1)+'周');
-->
</script>