/*

 check(ID)验证身份证号码

 返回值：0 : "是正确的身份证号"

         1 : "身份证校验不符合求和模11=1这个等式",

         2 : "身份证最后一位校验位有误",

         3 : "身份证位数不正确",

         4 : "年份错误",

         5 : "月份错误",

         6 : "日错误"

 */

 function check(ID) {

     var ck = new IDCard();

     ck.check(ID);

     return ck.errNum;

 }

 function IDCard(ID) {

     var me = this;

     this.checkCode = new Array(1, 0, 'X', 9, 8, 7, 6, 5, 4, 3, 2);

     this.ID;

     this.errNum = 0;

     this.err = {

         1 : "身份证校验不符合求和模11=1这个等式",

         2 : "身份证最后一位校验位有误",

         3 : "身份证位数不正确",

         4 : "年份错误",

         5 : "月份错误",

         6 : "日错误"

     };

     this.err_msg = function() {

         return (0 !== this.errNum) ? this.err[this.errNum] : null;

     };

     this.check = function(ID) {

         this.errNum = 0;

         this.ID = ID;

         if (cardValidate()) {

             if (!aiCheck()) this.errNum = 1;

             if (!LastByteCheck()) this.errNum = 2;

             return (0 === this.errNum) ? true: false;

         } else {

             return false;

         }

     };

     function getNum(str) {

         var re = /^[0]*([0-9]*)$/;

         str.match(re);

         return parseInt(RegExp.$1,10);

     }

     //对身份证位数，出生日期，初步验证

     function cardValidate() {

         var re = /^[0-9x]{15,18}$/i;

         if (!re.test(me.ID)) {

             me.errNum = 7;

             return false;

         }

         if (15 == me.ID.length || 18 == me.ID.length) {

             var realLen = 0;

             if (18 == me.ID.length) realLen = 2;

             var year = parseInt(me.ID.substr(6, 2 + realLen),10);

             var month = getNum(me.ID.substr(8 + realLen, 2));

             var day = parseInt(me.ID.substr(10 + realLen, 2),10);

             if (4 == year.length) if (year < 1900 || year > 2050) me.errNum = 4;

             if (month < 1 || month > 12) me.errNum = 5;

             if (day < 1 || day > 31) me.errNum = 6;

             return 0 === me.errNum;

         } else {

             me.errNum = 3;

             return false;

         }

     }

     //总和模11应该等于1

     var aiCheck = function() {

         var sum = 0;

         for (var i = 1; i <= me.ID.length; i++) {

             var ai = me.ID.substr(me.ID.length - i, 1);

             ai = (ai.toLowerCase() == 'x') ? 10 : ai;

             var wi = Math.pow(2, i - 1) % 11;

             sum += parseInt(ai,10) * wi;

         }

         return 1 == sum % 11;

     };

     //最后一位校验，这个可以和aiCheck合在一起，减少一次循环

     var LastByteCheck = function() {

         var sum = 0;

         for (var i = 2; i <= me.ID.length; i++) {

             var ai = me.ID.substr(me.ID.length - i, 1);

             ai = (ai.toLowerCase() == 'x') ? 10 : ai;

             var wi = Math.pow(2, i - 1) % 11;

             sum += parseInt(ai,10) * wi;

         }

         var checkCodeIndex = sum % 11;

         var c = me.ID.substr(me.ID.length - 1, 1);

         //alert(c+"=="+me.checkCode[checkCodeIndex]);

         return c == me.checkCode[checkCodeIndex];

     };

 }