credit card formatter

gistfile1.txt

var getFormattedValue = function (value, blocks, delimiter) {
        var result = '',
            currentDelimiter;

        var blocksLength = blocks.length;

        // no options, normal input
        if (blocksLength === 0) {
            return value;
        }

        blocks.forEach(function (length, index) {
            if (value.length > 0) {
                var sub = value.slice(0, length),
                    rest = value.slice(length);

                
                currentDelimiter = delimiter;
                
                result += sub;

                if (sub.length === length && index < blocksLength - 1) {
                    result += currentDelimiter;
                }

                // update remaining string
                value = rest;
            }
        });

        return result;
};

getFormattedValue("1234567812345678", [4,4,4,4])