Js regular second-generation ID card verification number

Generation ID number is fifteen, January 1, 2013 start, let's stop using the comprehensive Chinese generation ID card.

Second-generation ID number:

• 1-6: Codes administrative divisions.
  • 1,2 position, where the provinces (municipalities and autonomous regions) Code;
  • 3,4 position, location-level cities (Autonomous) Code;
  • 5,6 position, where the district (counties, autonomous counties, county-level cities) of the Code;
• 7 - 14 bit: that birth year, month, day
• 15-16 place: the police station where the code
• 17: sex. An odd number (1,3,5,7,9) male, even number (2,4,6,8,0) Women
• 18: parity bit, the presence of eleven values: 0,1,2,3,4,5,6,7,8,9, X, which is a fixed value calculated from the formula of the preceding seventeen.

The eighteenth bit number is ISO 7064: calculated checksum algorithm 1983.MOD 11-2

// 函数参数必须是字符串，因为二代身份证号码是十八位，而在javascript中，十八位的数值会超出计算范围，造成不精确的结果，导致最后两位和计算的值不一致，从而该函数出现错误。
// 详情查看javascript的数值范围
function checkIDCard(idcode){
    // 加权因子
    var weight_factor = [7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2];
    // 校验码
    var check_code = ['1', '0', 'X' , '9', '8', '7', '6', '5', '4', '3', '2'];

    var code = idcode + "";
    var last = idcode[17];//最后一位

    var seventeen = code.substring(0,17);

    // ISO 7064:1983.MOD 11-2
    // 判断最后一位校验码是否正确
    var arr = seventeen.split("");
    var len = arr.length;
    var num = 0;
    for(var i = 0; i < len; i++){
        num = num + arr[i] * weight_factor[i];
    }
    
    // 获取余数
    var resisue = num%11;
    var last_no = check_code[resisue];

    // 格式的正则
    // 正则思路
    /*
    第一位不可能是0
    第二位到第六位可以是0-9
    第七位到第十位是年份，所以七八位为19或者20
    十一位和十二位是月份，这两位是01-12之间的数值
    十三位和十四位是日期，是从01-31之间的数值
    十五，十六，十七都是数字0-9
    十八位可能是数字0-9，也可能是X
    */
    var idcard_patter = /^[1-9][0-9]{5}([1][9][0-9]{2}|[2][0][0|1][0-9])([0][1-9]|[1][0|1|2])([0][1-9]|[1|2][0-9]|[3][0|1])[0-9]{3}([0-9]|[X])$/;

    // 判断格式是否正确
    var format = idcard_patter.test(idcode);

    // 返回验证结果，校验码和格式同时正确才算是合法的身份证号码
    return last === last_no && format ? true : false;
}