Getting issue while fetching data from mongodb using async/await

Question

I am using node.js express framework to create REST API and trying to convert my code from callbacks to Async/Await methods with basic .then() promise using artical . so while implementing code getting error as SyntaxError: await is only valid in async function

I am new to javascript and not understand what is cause this issue. I have below folder structure

 MAIN APP
    ├── app.js
    ├── controllers
    │   └── UserController.js
    ├── routes
    │   └── User.js
    └── util
        ├── AuthUtil.js
        ├── Helpers.js
        ├── RestUtil.js
        └── wallet.js

My backend API controller function is below

Getone: async (req, res, next) => {
    try {
    MongoClient.connect(config.Database.DFARM.connectString, function(err, client) {
       assert.equal(null, err);
       const db = client.db(config.Database.DFARM.dbName);
      console.log('********db**********',db)
       //Step 1: declare promise

        var myPromise = () => {
           return new Promise((resolve, reject) => {

              db
              .collection('User')
              .find(query)
              .limit(1)
              .toArray(function(err, docs) {
                 err
                    ? reject(err)
                    : resolve(docs[0]);
               });
           });
        };
       //await myPromise
       var result = await myPromise();
       //continue execution
       client.close();
       console.log('********result**********',result)

    //    res.json(result);
    }); //end mongo client
    } catch (e) {
       next(e)
    }
    }

My router

router.get('/getone/:id', function (req, res, next) {
    controller.Getone(req, res, next);
});

Yakir Fitousi · Accepted Answer · 2020-10-22 20:29:13Z

2

So, basically the nested function is not async. so you need to:

async function(err, client) {/* your code */}

BTW, why are you constructing new promise inside the async function? you can just do the next:

Getone: async (req, res, next) => {
  try {
   const client = await MongoClient.connect(config.Database.DFARM.connectString)
   const db = client.db(config.Database.DFARM.dbName);
   const result = await db
          .collection('User')
          .find(query)
          .limit(1)
          .toArray(function(err, docs) {
             err
                ? reject(err)
                : resolve(docs[0]);
           });
       });
   // do something with result..
   client.close();
   console.log('********result**********',result)
  } catch (error) {
    // handle error
  } 
};

edited Oct 22, 2020 at 20:29

answered Oct 20, 2020 at 20:52

Yakir Fitousi

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1 Comment

Abhijeet1234 Over a year ago

Thanks@Yakir for suggestion and help

gillall · Accepted Answer · 2020-10-20 19:31:40Z

1

The function "function (err, client)" are not async and you are using await inside. So you get this error. Try "async function (err, client)"

answered Oct 20, 2020 at 19:31

gillall

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