JavaScript实现年月日与星期级联选择功能

<html> 
  <head> 
    <meta http-equiv="Content-Type" content="text/html; charset=GB2312"> 
    <title>年月日星期级联</title> 
  </head> 
 
  <body topmargin="10" leftmargin="0"> 
    <form> 
      <select id=year onchange="toDate();"> 
        <script>for(i=1970;i<=2010;i++)document.write("<option>"+i+"</option>")</script> 
      </select> 
      <select id=month onchange="toDate();"> 
        <script>for(i=1;i<=12;i++)document.write("<option>"+i+"</option>")</script> 
      </select> 
      <select id=day onchange="toDay();"></select> 
      <input name=weekday> 
    </form> 
    <script type="text/javascript"> 
      var arr="日一二三四五六".split("") 
      function toDate(){ 
        with(document.all){ 
          vYear=parseInt(year.options[year.selectedIndex].text) 
          vMonth=parseInt(month.options[month.selectedIndex].text) 
          day.length=0; 
          for(i=0;i<(new Date(vYear,vMonth,0)).getDate();i++){day.options[day.length++].value=day.length;day.options[day.length-1].text=day.length;} 
        } 
        toDay(); 
      } 
      function toDay(){ 
        vDay=parseInt(document.all.day.options[document.all.day.selectedIndex].value) 
        document.all("weekday").value="星期"+arr[new Date(vYear,vMonth-1,vDay).getDay()] 
      } 
      window.onload=toDate; 
    </script> 
  </body> 
</html>