Validates slovak ID identifiers

validateSkId.js

/*
     * validates slovak ID numbers 
     * 
     * @param string skIdNumber slovak ID number 
     *
     * @return bool
     */
    function validateSkId (skIdNumber) {
        if (skIdNumber == undefined || 
            skIdNumber.length < 1 || 
            skIdNumber == null){
            return false;
        }
        // remove all spaces from string
        skIdNumber = skIdNumber.replace(/\s+/g, '');
        
        //check length after space removal
        if (skIdNumber.length != 8){
            return false;
        }
    
        // AA XXXXXX - two characters + 6 numbers    
        var re = /([a-zA-Z]){2}([0-9]){6}/;
        
        return re.test(skIdNumber);
    }