Validate Danish CPR

validate-cpr.js

//  Validate CPR-nr.
function is_cpr_valid(cpr) {

    var res = cpr.replace(/[^0-9]/ig, "");
    
    if (res.length != 10) {
        return false;
    }

    var validDates = ['010165', '010166', '010170', '010180', '010187', '010190'];

    var value = res.substr(0, 6);

    if (contains(validDates, value)) {
        return true;
    }

    var cpr_arr = res.split('');
    var mul_arr = "4327654321".split('');
    
    var sum = 0;
    for (var i = 0; i < cpr_arr.length; i++) {
        sum += cpr_arr[i] * mul_arr[i];
    }

    if (sum % 11 == 0) {
        return true;
    } else {
        return false;
    }

    return true;
}