直接上代码，逐行对代码进行研究，一定会有所收获。
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; } 使用方法：
<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> 希望本文对大家学习javascript程序设计有所帮助。