Obfuscate credit card number in AngularJS

/**
 * Format for a Credit Card
 * @return {string} Formatted number
 */
module.filter("creditcard", function() {
    return function(str) {
        if(typeof str !== "undefined"){
            var nums = str.substr(0,19).replace(/[^\d]/gi,"");
            var r = nums.match(/(\d){4}/g);
            r[1] = r[1].replace(/[0-9]/g, "*");
            r[2] = r[2].replace(/[0-9]/g, "*");
            r = r.slice(0,5);
            if(r){
                var nStr = "", nums;
                for (var i=0;i<r.length;i++){
                    nStr += i != r.length-1 ? r[i] + ((i<3)?" ":"") : r[i];
                }
                nums = (nums.length % 4 !== 0 ? nStr + " " + nums.substr((r.length * 4),nums.length) : nStr);
                str = nums;
            } else {
                str = nums;
            }
            return str;
        }
    };
});