JS根据身份证号提取出生日期并计算年龄

<script>
function getAge(){
var   aDate=new   Date();  
  var   thisYear=aDate.getYear();
var brith=document.getElementById("date1").value;
brith=brith.substr(0,4);
age=(thisYear-brith);
document.getElementById("date2").value=age;
}

function ExtractionBirthday(oneText,twoText){
  var txtparm = document.getElementById(oneText).value;
  if(txtparm.length==18){
 　　var year = txtparm.substring(6,10);
 　　var month = txtparm.substring(10,12);
 　　var date=txtparm.substring(12,14);
 　　document.getElementById(twoText).value=year+"-"+month+"-"+date;
  }else{
  　　alert("输入的身份证不正确！");
  　　document.getElementById(oneText).focus();
  　　document.getElementById(oneText).value="";
  }
}

 

</script>
<from name="theform">
生日:<input name="date1" id="date1" onblur="getAge()">
年龄:<input name="date2" id="date2">

身份证：<input id="A" type="text"  onblur="ExtractionBirthday('A','B');"/>

出生日期：<input id="B" type="text"/>

</form></font>