define(['./filter'], function(filter) {

    function isValidString(val) {
        return (val != null && val !== '');
    }

    /**
     * Joins strings with the specified separator inserted between each value.
     * Null values and empty strings will be excluded.
     */
    function join(items, separator) {
        separator = separator || '';
        return filter(items, isValidString).join(separator);
    }

    return join;
});