身份证校验（支持15位和18位身份证号）

//身份证号合法性验证
//支持15位和18位身份证号
//支持地址编码、出生日期、校验位验证

function IdentityCodeValid(code) {
  var city = {
    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 "
  };
  var tip = "";
  var pass = true;
  //验证身份证格式（6个地区编码，8位出生日期，3位顺序号，1位校验位）
  if (!code || !/^[1-9]\d{7}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}$|^[1-9]\d{5}[1-9]\d{3}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}([0-9]|X)$/.test(code)) {
    tip = "身份证号格式错误";
    pass = false;
  } else if (!city[code.substr(0, 2)]) {
    tip = "地址编码错误";
    pass = false;
  } else {
    //18位身份证需要验证最后一位校验位
    if (code.length == 18) {
      code = code.split('');
      //∑(ai×Wi)(mod 11)
      //加权因子
      var factor = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
      //校验位
      var parity = [1, 0, 'X', 9, 8, 7, 6, 5, 4, 3, 2];
      var sum = 0;
      var ai = 0;
      var wi = 0;
      for (var i = 0; i < 17; i++) {
        ai = code[i];
        wi = factor[i];
        sum += ai * wi;
      }
      var last = parity[sum % 11];
      if (parity[sum % 11] != code[17]) {
        tip = "校验位错误";
        pass = false;
      }
    }
  }
  return pass;
}