function nunber(allowancePersonValue){ 
 if(allowancePersonValue=="身份证号"){ 
 $("#span_username").show(); 
 $("#span_username").html("身份证号不能为空"); 
 return false; 
 } 
 //校验长度，类型 
 else if(isCardNo(allowancePersonValue) === false) 
 { 
$("#span_username").show(); 
 $("#span_username").html("您输入的身份证号码不正确，请重新输入"); 
 return false; 
 } 
 //检查省份 
 else if(checkProvince(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您输入的身份证号码不正确,请重新输入"); 
 return false; 
 } 
 //校验生日 
 else if(checkBirthday(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您输入的身份证号码生日不正确,请重新输入"); 
 return false; 
 } 
 //检验位的检测 
 else if(checkParity(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您的身份证校验位不正确,请重新输入"); 
 return false; 
 }else{ 
 $("#span_username").hide(); 
 return true; 
 } 
 
} 
 
//身份证省的编码 
var vcity={ 11:"北京",12:"天津",13:"河北",14:"山西",15:"内蒙古", 
    21:"辽宁",22:"吉林",23:"黑龙江",31:"上海",32:"江苏", 
    33:"浙江",34:"安徽",35:"福建",36:"江西",37:"山东",41:"河南", 
    42:"湖北",43:"湖南",44:"广东",45:"广西",46:"海南",50:"重庆", 
    51:"四川",52:"贵州",53:"云南",54:"西藏",61:"陕西",62:"甘肃", 
    63:"青海",64:"宁夏",65:"新疆",71:"台湾",81:"香港",82:"澳门",91:"国外" 
    }; 
 
//检查号码是否符合规范，包括长度，类型 
function isCardNo(card){ 
 //身份证号码为15位或者18位，15位时全为数字，18位前17位为数字，最后一位是校验位，可能为数字或字符X 
 var reg = /(^\d{15}$)|(^\d{17}(\d|X)$)/; 
 if(reg.test(card) === false){ 
 //alert("demo"); 
 return false; 
 } 
 return true; 
} 
 
//取身份证前两位,校验省份 
function checkProvince(card){ 
 var province = card.substr(0,2); 
 if(vcity[province] == undefined){ 
 return false; 
 } 
 return true; 
} 
 
//检查生日是否正确 
function checkBirthday(card){ 
 var len = card.length; 
 //身份证15位时，次序为省（3位）市（3位）年（2位）月（2位）日（2位）校验位（3位），皆为数字 
 if(len == '15'){ 
   var re_fifteen = /^(\d{6})(\d{2})(\d{2})(\d{2})(\d{3})$/; 
   var arr_data = card.match(re_fifteen); 
   var year = arr_data[2]; 
   var month = arr_data[3]; 
   var day = arr_data[4]; 
   var birthday = new Date('19'+year+'/'+month+'/'+day); 
   return verifyBirthday('19'+year,month,day,birthday); 
 } 
 //身份证18位时，次序为省（3位）市（3位）年（4位）月（2位）日（2位）校验位（4位），校验位末尾可能为X 
 if(len == '18'){ 
   var re_eighteen = /^(\d{6})(\d{4})(\d{2})(\d{2})(\d{3})([0-9]|X)$/; 
   var arr_data = card.match(re_eighteen); 
   var year = arr_data[2]; 
   var month = arr_data[3]; 
   var day = arr_data[4]; 
   var birthday = new Date(year+'/'+month+'/'+day); 
   return verifyBirthday(year,month,day,birthday); 
 } 
 return false; 
} 
 
//校验日期 
function verifyBirthday(year,month,day,birthday){ 
 var now = new Date(); 
 var now_year = now.getFullYear(); 
 //年月日是否合理 
 if(birthday.getFullYear() == year && (birthday.getMonth() + 1) == month && birthday.getDate() == day) 
 { 
   //判断年份的范围（3岁到100岁之间) 
   var time = now_year - year; 
   if(time >= 3 && time <= 100) 
   { 
     return true; 
   } 
   return false; 
 } 
 return false; 
} 
 
//校验位的检测 
function checkParity(card){ 
 //15位转18位 
 card = changeFivteenToEighteen(card); 
 var len = card.length; 
 if(len == '18'){ 
   var arrInt = new Array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2); 
   var arrCh = new Array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'); 
   var cardTemp = 0, i, valnum; 
   for(i = 0; i < 17; i ++) 
   { 
     cardTemp += card.substr(i, 1) * arrInt[i]; 
   } 
   valnum = arrCh[cardTemp % 11]; 
   if (valnum == card.substr(17, 1)) 
   { 
     return true; 
   } 
   return false; 
 } 
 return false; 
} 
 
//15位转18位身份证号 
function changeFivteenToEighteen(card){ 
 if(card.length == '15') 
 { 
   var arrInt = new Array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2); 
   var arrCh = new Array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'); 
   var cardTemp = 0, i;  
   card = card.substr(0, 6) + '19' + card.substr(6, card.length - 6); 
   for(i = 0; i < 17; i ++) 
   { 
     cardTemp += card.substr(i, 1) * arrInt[i]; 
   } 
   card += arrCh[cardTemp % 11]; 
   return card; 
 } 
 return card; 
} 

<input type="text" class="reg_txt" value="身份证号" titles="请输入您的身份证号！" name="userid" id="username" maxlength="40" onfocus="if(this.value=='身份证号'){this.value='';}" onblur="if(this.value==''){this.value='身份证号';}nunber(this.value);" style="border: 1px solid red;"><br> 
<span class="c_red" id="span_username"></span>