Nodejs with Mysql Database Return value

Question

I have the following code. I am relative new to nodejs &js

I want to get values in 1. log but i get undefined. Only 2. log is outputed to the log.

I read nodeJS return value from callback and https://github.com/felixge/node-mysql but there is no example about return value.

I donot know how to use return statement with the given example in node-mysql page.

exports.location_internal = function (req, res) {
    var r = getExternalLocation(2);
        // 1. log  
    console.log(r);
    res.send( r);
}

var getExternalLocation = function (id) {
    pool.getConnection(function(err, connection){
      if(err) throw err;

      var response = {};
      connection.query( "select * from external_geo_units where geo_unit_id = "+id,  function(err, rows){
        if(err) throw err;
        response.data= rows;
                // 2. log
        console.log(response);
        return  response;
      });
      connection.release();
    });

};

Answer 1

It's asynchronous, so you have to pass in a callback to get the value when it's ready. Example:

exports.location_internal = function(req, res, next) {
  getExternalLocation(2, function(err, rows) {
    if (err)
      return next(err);
    console.log(rows);
    res.send(rows);
  });
};

function getExternalLocation(id, cb) {
  pool.getConnection(function(err, conn) {
    if (err)
      return cb(err);

    conn.query("select * from external_geo_units where geo_unit_id = ?",
               [id],
               function(err, rows) {
      conn.release();
      cb(err, rows);
    });
  });
}