function luhuCheck(sCardNum) {
    var iOddSum = 0;
    var iEvenSum = 0;
    var bIsOdd = true;
    for(var i = sCardNum.length-1; i >= 0; i --){
        var iNum = parseInt(sCardNum.charAt(i));
        if(bIsOdd){
            iOddSum += iNum;
        }else{
            iNum = iNum * 2;
            if(iNum > 9){
                iNum = eval(iNum.toString().split('').join('+'));
             }
            iEvenSum += iNum;
        }
        bIsOdd = !bIsOdd;
    }
    return (iEvenSum + iOddSum) % 10 == 0;
}
//javascript/7090