无限扩展的年份select

var Lastyear 
function selYear(obj,Cyear){ 
var len=16 //select长度 
var selObj=document.getElementById(obj) 
var selIndex=parseInt(len/2)-1 
var newOpt 
var LY=Cyear-Lastyear 
for (i=0;i<len;i++){ 
   if (selObj.options.length!=len){ 
     newOpt=document.createElement("OPTION") 
     newOpt.text=Cyear-selIndex+i 
     newOpt.value=Cyear-selIndex+i 
     selObj.options.add(newOpt,i) 
      if (selIndex==i) {Lastyear=newOpt.value}       
     } 
    else 
    { 
     selObj.options[i].text=parseInt(selObj.options[i].text)+LY 
     selObj.options[i].value=parseInt(selObj.options[i].value)+LY 
     if (selIndex==i) {Lastyear=selObj.options[i].value}            
    } 
 } 
  selObj.selectedIndex=selIndex 
} 
</script> 
<select size="1" id="yearSelect" name="yearSelect" onchange="selYear('yearSelect',this.value)"></select> 
<script>selYear('yearSelect',2005) //初试化select</script>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]