sim 卡校验 luhn 算法

sim 卡最后一位为校验位，以下为 js 算法

function luhmCheck(bankno) {
    var lastNum = bankno.substr(bankno.length - 1, 1); //取出最后一位（与luhm进行比较）
    var first15Num = bankno.substr(0, bankno.length - 1); //前15或18位
    var newArr = new Array();
    for (var i = first15Num.length - 1; i > -1; i--) { //前15或18位倒序存进数组
        newArr.push(first15Num.substr(i, 1));
    }
    var arrJiShu = new Array(); //奇数位*2的积 <9
    var arrJiShu2 = new Array(); //奇数位*2的积 >9
    var arrOuShu = new Array(); //偶数位数组
    for (var j = 0; j < newArr.length; j++) {
        if ((j + 1) % 2 == 1) { //奇数位
            if (parseInt(newArr[j]) * 2 < 9) arrJiShu.push(parseInt(newArr[j]) * 2);
            else arrJiShu2.push(parseInt(newArr[j]) * 2);
        } else //偶数位
        arrOuShu.push(newArr[j]);
    }

    var jishu_child1 = new Array(); //奇数位*2 >9 的分割之后的数组个位数
    var jishu_child2 = new Array(); //奇数位*2 >9 的分割之后的数组十位数
    for (var h = 0; h < arrJiShu2.length; h++) {
        jishu_child1.push(parseInt(arrJiShu2[h]) % 10);
        jishu_child2.push(parseInt(arrJiShu2[h]) / 10);
    }

    var sumJiShu = 0; //奇数位*2 < 9 的数组之和
    var sumOuShu = 0; //偶数位数组之和
    var sumJiShuChild1 = 0; //奇数位*2 >9 的分割之后的数组个位数之和
    var sumJiShuChild2 = 0; //奇数位*2 >9 的分割之后的数组十位数之和
    var sumTotal = 0;
    for (var m = 0; m < arrJiShu.length; m++) {
        sumJiShu = sumJiShu + parseInt(arrJiShu[m]);
    }

    for (var n = 0; n < arrOuShu.length; n++) {
        sumOuShu = sumOuShu + parseInt(arrOuShu[n]);
    }

    for (var p = 0; p < jishu_child1.length; p++) {
        sumJiShuChild1 = sumJiShuChild1 + parseInt(jishu_child1[p]);
        sumJiShuChild2 = sumJiShuChild2 + parseInt(jishu_child2[p]);
    }
    //计算总和
    sumTotal = parseInt(sumJiShu) + parseInt(sumOuShu) + parseInt(sumJiShuChild1) + parseInt(sumJiShuChild2);

    //计算Luhm值
    var k = parseInt(sumTotal) % 10 == 0 ? 10 : parseInt(sumTotal) % 10;
    var luhm = 10 - k;

    if (lastNum == luhm) {
        return true;
    } else {
        return false;
    }
}

function luhm(num) {
    if (typeof num == 'object') {
        var re = [];
        for (var k in num) {
            re.push((num[k]).toString() + luhm(num[k]));
        }
        return re;
    } else {
        for (var i = 0; i <= 9; i++) {
            if (luhmCheck(num + i)) {
                return i
            }
        }
    }
}