Convert Promise to async-CodePudding

I am trying to convert mySQL connection from promise to asycn await so far I have the following setup:

const mysql = require("mysql");

const pool = mysql.createPool({
  connectionLimit: 10,
  password: "",
  user: "root",
  database: "usersdb",
  host: "localhost",
  port: "3306",
});

let usersDB = {};

usersDB.all = () => {
  return new Promise((resolve, reject) => {
    pool.query("SELECT * FROM users", (err, results) => {
      if (err) {
        return reject(err);
      }

      return resolve(results);
    });
  });
};

usersDB.one = (id) => {
  return new Promise((resolve, reject) => {
    pool.query("SELECT * FROM users WHERE id = ?", [id], (err, results) => {
      if (err) {
        return reject(err);
      }

      return resolve(results[0]);
    });
  });
};

module.exports = usersDB;

Is there a way to convert this codes:

return new Promise((resolve, reject) => {
    pool.query("SELECT * FROM users", (err, results) => {
      if (err) {
        return reject(err);
      }

      return resolve(results);
    });

to async await and make the code more compress or succint?

UPDATE: on my router, I have these codes:

const router = express.Router();

router.get("/", async (req, res) => {
  try {
    let results = await db.all();
    res.json(results);
  } catch (error) {
    console.log(error);
    res.sendStatus(500);
  }
});

router.get("/:id", async (req, res) => {
  try {
    let results = await db.one(req.params.id);
    res.json(results);
  } catch (error) {
    console.log(error);
    res.sendStatus(500);
  }
});

So it just fine calling async await twice?

CodePudding user response：

You can convert any callback function to promise by using util.promisify

const util = require('util')
// ....
const query = util.promisify(pool.query)



// ... inside some async function
const users = await query("SELECT * FROM users;")


// or promise style
query("SELECT * FROM users;")
   .then((users) => {
      console.log(users)
    })
    .catch(console.error)

CodePudding user response：

usersDB.one = (id) => {
    try {
        const users = pool.query("SELECT * FROM users WHERE id = ?", [id]);
        return users;
    } catch (e) {
        throw e;
    }
};

Or more simply,

usersDB.one = (id) => pool.query("SELECT * FROM users WHERE id = ?", [id]);

CodePudding user response：

What you want to do is to promisify the DB call. You can acheive this by factorisation :


const mysql = require("mysql");

const pool = mysql.createPool({
  connectionLimit: 10,
  password: "",
  user: "root",
  database: "usersdb",
  host: "localhost",
  port: "3306",
});

function promisify(...args){
    return new Promise((resolve, reject) => {
        pool.query(...args, (err, result) => {
            if(err) reject(err);
            resolve(result);
        });
    });
}

let usersDB = {};

//Then you can call it this way : 

usersDB.all = async () => {
    return await promisify("SELECT * FROM users");
   //Note that you can avoid to await there.
};

usersDB.one = async (id) => {
    return await promisify("SELECT * FROM users WHERE id = ?", [id]);
};

module.exports = usersDB;