function nunber(allowancePersonValue){ 
 if(allowancePersonValue=="身份證號"){ 
 $("#span_username").show(); 
 $("#span_username").html("身份證號不能為空"); 
 return false; 
 } 
 //校驗長度，類型 
 else if(isCardNo(allowancePersonValue) === false) 
 { 
$("#span_username").show(); 
 $("#span_username").html("您輸入的身份證號碼不正確，請重新輸入"); 
 return false; 
 } 
 //檢查省份 
 else if(checkProvince(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您輸入的身份證號碼不正確,請重新輸入"); 
 return false; 
 } 
 //校驗生日 
 else if(checkBirthday(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您輸入的身份證號碼生日不正確,請重新輸入"); 
 return false; 
 } 
 //檢驗位的檢測 
 else if(checkParity(allowancePersonValue) === false) 
 { 
 $("#span_username").show(); 
 $("#span_username").html("您的身份證校驗位不正確,請重新輸入"); 
 return false; 
 }else{ 
 $("#span_username").hide(); 
 return true; 
 } 
 
} 
 
//身份證省的編碼 
var vcity={ 11:"北京",12:"天津",13:"河北",14:"山西",15:"內蒙古", 
    21:"遼寧",22:"吉林",23:"黑龍江",31:"上海",32:"江蘇", 
    33:"浙江",34:"安徽",35:"福建",36:"江西",37:"山東",41:"河南", 
    42:"湖北",43:"湖南",44:"廣東",45:"廣西",46:"海南",50:"重慶", 
    51:"四川",52:"貴州",53:"云南",54:"西藏",61:"陜西",62:"甘肅", 
    63:"青海",64:"寧夏",65:"新疆",71:"臺灣",81:"香港",82:"澳門",91:"國外" 
    }; 
 
//檢查號碼是否符合規(guī)范，包括長度，類型 
function isCardNo(card){ 
 //身份證號碼為15位或者18位，15位時全為數(shù)字，18位前17位為數(shù)字，最后一位是校驗位，可能為數(shù)字或字符X 
 var reg = /(^\d{15}$)|(^\d{17}(\d|X)$)/; 
 if(reg.test(card) === false){ 
 //alert("demo"); 
 return false; 
 } 
 return true; 
} 
 
//取身份證前兩位,校驗省份 
function checkProvince(card){ 
 var province = card.substr(0,2); 
 if(vcity[province] == undefined){ 
 return false; 
 } 
 return true; 
} 
 
//檢查生日是否正確 
function checkBirthday(card){ 
 var len = card.length; 
 //身份證15位時，次序為?。?位）市（3位）年（2位）月（2位）日（2位）校驗位（3位），皆為數(shù)字 
 if(len == '15'){ 
   var re_fifteen = /^(\d{6})(\d{2})(\d{2})(\d{2})(\d{3})$/; 
   var arr_data = card.match(re_fifteen); 
   var year = arr_data[2]; 
   var month = arr_data[3]; 
   var day = arr_data[4]; 
   var birthday = new Date('19'+year+'/'+month+'/'+day); 
   return verifyBirthday('19'+year,month,day,birthday); 
 } 
 //身份證18位時，次序為?。?位）市（3位）年（4位）月（2位）日（2位）校驗位（4位），校驗位末尾可能為X 
 if(len == '18'){ 
   var re_eighteen = /^(\d{6})(\d{4})(\d{2})(\d{2})(\d{3})([0-9]|X)$/; 
   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; 
} 
 
//校驗日期 
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) 
 { 
   //判斷年份的范圍（3歲到100歲之間) 
   var time = now_year - year; 
   if(time >= 3 && time <= 100) 
   { 
     return true; 
   } 
   return false; 
 } 
 return false; 
} 
 
//校驗位的檢測 
function checkParity(card){ 
 //15位轉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位轉18位身份證號 
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="身份證號" titles="請輸入您的身份證號！" name="userid" id="username" maxlength="40" onfocus="if(this.value=='身份證號'){this.value='';}" onblur="if(this.value==''){this.value='身份證號';}nunber(this.value);" style="border: 1px solid red;"><br> 
<span class="c_red" id="span_username"></span>