Validate NIP

isNIPvalid.js

/*
Check for validity of polish VAT ID number: NIP
*/

function NIPIsValid(nip) {
        var weights = [6, 5, 7, 2, 3, 4, 5, 6, 7];
        nip = nip.replace(/[\s-]/g, '');
 
        if (nip.length == 10 && parseInt(nip, 10) > 0) {
                var sum = 0;
                for(var i = 0; i < 9; i++){
                        sum += nip[i] * weights[i];
                }                     
                return (sum % 11) == nip[9];
        }
        return false;           
}