Node.js Using async/await with mysql

Question

I've been trying to use async/await with MySQL in node but it returns an undefined value each time. Is there a reason why? Please find my code below.

const mysql = require('promise-mysql');

    var connection;

    const dbConfig = {
        host: "hostname",
        database: "dbname",
        user: "username",
        password: "passwords"
    };

    async function getResult(){

        await mysql.createConnection(dbConfig).then(function(conn){

            connection = conn;
            var result = connection.query('select height from users where pin=1100');

            return result;

        }).then(function(rows){
            console.log(JSON.parse(JSON.stringify(rows[0].height)));
            connection.end();
            return rows[0].height;
        }).catch(function(error){
            if (connection && connection.end) connection.end();
            //logs out the error
            console.log(error);
        });
    }


    async function queryDb(){

        try{

         var height = await getResult(); 
        console.log(height);
         if(height){
            console.log(height)
         }

        }catch(err){
            console.log(err);
            console.log('Could not process request due to an error');
            return;

        }
    }

    queryDb();

I expect the height to be returned in queryDb, however, the value is only shown in the getResult function and not returned to be used in the queryDb function.

I know the code may not be perfect as I'm new to node and I've been trying to find alternative ways to do this but

Your `getResult` function doesn't return anything. – Aug 23 '18 at 12:04 — , Aug 23 '18 at 12:04
@ChrisG Thank you, that was very silly on my part – Jay Aug 23 '18 at 12:09 — Jay, Aug 23 '18 at 12:09

Evert · Answer 1 · 2018-08-23T12:31:27.247

async function getResult(){

    let connection;
    try {

      connection = await mysql.createConnection(dbConfig);
      const result = await connection.query('select height from users where pin=1100');

      console.log(result[0].height);
      return result[0].height;

    } finally {
      if (connection && connection.end) connection.end();
    }

}

Fixes the following problems:

If you can use async/await, it's pointless to still use then for these situations..
You don't need to JSON stringify and parse if you're logging something.
If you catch an error to close a connection, you really should rethrow it so the function that calls getResult doesn't get garbage/undefined back. Instead of rethrowing it, I just added a finally block that always closes the connection, whether it was successful or not.
Since you're using async/await, your javascript engine should support let and const. It's better than var =)
You weren't returning anything.

Thank you for your help. The code worked after I actually returned something at the end. Your edition is insightful but didn't work due to the rows not being recorded. — Jay, Aug 23 '18 at 12:18

Node.js Using async/await with mysql

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