Loopback custom remote method how to do a full text search?

I have created index now want to do a full text search along with a where condition, Suppose i want to search a term and check if the expireDate is not expired, so it should search the search term only inside those documents that are not expired. What I have tried is:

 JobPosting
    .find(
        { $text : { $search : searchTerm } },
        { score : { $meta: "textScore" } }
    )
    .sort({ score : { $meta : 'textScore' } })
    .exec(function(err, results) {
      console.log(results)
      // callback
    });

But above code has problem, sort() and exec() is not a function, and the second problem is with where condition. How i can check expireDate? If i remove sort() and exec() bring the wrong result (bring all result).

via jones