async await not working with callback node (without promise)

Question

hello guys i got confused why this not working here is my connection js file

    function getConnection(callback) {
        initPool()
        mysql_pool.getConnection((err, conn) => {
            if (err) {
                return callback(err);
            }
               return callback(err, conn);
        });
     }

    function query(queryString, callback) {

        getConnection((err, connection2) => {
            if (connection2 != undefined) {
                if (err) {
                    connection2.destroy();
                return  callback(createDataResponseObject(err, null))
                }
                connection2.query(queryString, function (err, rows) {
                    connection2.destroy();
                    if (!err) {
                        return callback(createDataResponseObject(err, rows))
                    }
                    else {
                        return callback(createDataResponseObject(err, null))
                    }
                });                   
            }

        });
    }
    function createDataResponseObject(error, results) {
        if (error) {
            logger.info(error);
        }
        return {
            error: error,
            results: results === undefined ? null : results === null ? null : results
        }
    }

now when i acquire this connection js in my router.js below is sample code

   var conn=require("./connection")
   router.post('/test',async function(res,req){
      var query ="select * from users"
      let x= await conn.query(result);
      console.log(x)        
   });

in connection js file i haven't use promise then why async not working in router i.e it should still work because i m using callback can anyone tell me what i m missing or what i m doing wrong. when i tried it with return promise in connection.js file it working. i know async return promise

score 5 · Accepted Answer · answered Dec 10 '18 at 14:16

5

You can only await a promise. conn.query doesn't return a promise. It has no return statement: It returns undefined.

You need to promisify your database functions.

answered Dec 10 '18 at 14:16

Quentin

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that mean it will not work which i had used in connection.js file i.e i have to return promise from function query ??? – bipin Dec 10 '18 at 14:23
@bipin — Yes, that's what I said. – Quentin Dec 10 '18 at 14:24

score 3 · Answer 2 · answered Dec 10 '18 at 14:16

3

Async/await only works with promises, it’s a syntactic sugar on top of it. I.e. you can’t use the syntax with callbacks.

Check out this link: https://javascript.info/async-await

answered Dec 10 '18 at 14:16

busyfingers

89
3

score 1 · Answer 3 · answered Dec 10 '18 at 14:17

Async only works with promises, to get things working you have to first convert all of your function to return promises. You can use Promise.promisify() to convert all callback style function to return a promise. Once it is done you can use these function with async-await.

async await not working with callback node (without promise)

3 Answers3

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