JS正则表达式实现手机号码和省份证号码校验

<script type="text/javascript">
function checkform() {

var re;
var ss = document.getElementById('txtMobile').value;
re = /^(1[358][0-9]{9})$/;
if (re.test(ss)==false) {
alert("手机号码输入不合法");
return false;
}

var id=document.getElementById("txtIDNUMBER").value;
var reg = /(^\d{15}$)|(^\d{18}$)|(^\d{17}(\d|X|x)$)/;
if (reg.test(id) === false) {
alert("身份证输入不合法");
return false;
}

}
</script>