Q.js Promise With Node. Missing Error Handler On `socket`. Typeerror: Cannot Call Method 'then' Of Undefined

I´m rookie with nodejs and with promises, I installed Q.js with npm : npm install q I´m try yo make a promise when I made a query to postgres, this is my code... socket.on('Oper

Solution 1:

Refer to q.defer example, please try to move return deferred.promise; out of client.query as below

functiongetElementInPostgres(makeQuery){
  console.log("entro getElementInPostgres");
  var deferred = Q.defer();
  client.query( makeQuery,
                  function(err, result) {
                    if (err) {
                       console.log("NO getElementInPostgres");
                      console.log(err);
                      deferred.reject(err);
                    } else {
                       console.log("ok getElementInPostgres");
                     console.log(result);
                     deferred.resolve(result);
                    }
                });
     return deferred.promise;
}

Solution 2:

You just have to return the promise outside client.query..

functiongetElementInPostgres(makeQuery){
    console.log("entro getElementInPostgres");
    var deferred = Q.defer();
    client.query(makeQuery, function(err, result) {
        if (err) {
            console.log("NO getElementInPostgres");                               
            console.log(err);
            deferred.reject(err);
        } else {
            console.log("ok getElementInPostgres");
            console.log(result);
            deferred.resolve(result);
        }
    });
    return deferred.promise;
}

client.query is an async method....so when you call

getElementInProgress(makeQuery).then(...);

the .then() will be called before client.query returns.