also 

    results = ('limit' in opts) ? results.slice(opts.skip, opts.limit + opts.skip) : 
        (opts.skip > 0) ? results.slice(opts.skip) : results

or something similiar, with nested ternary operators its best if the line always starts with either the condition or the falsey or the truthy result, but not all mixed up, if they cant be split up like that then can just use an if