JavaScript(node.js) - async await does not work

Question

I have some problems using async/await. If i call getAccountDetails i only get undefined and afterwards i get the log

getOpengraphResponse is ok

But i use async/await. And request is request-promise-native. At position one should be the log

getOpengraphResponse is ok

and then the property details should be displayed. Where is my mistake?

const https = require('https');
const request = require('request-promise-native');
let openGraphBaseURL = "https://graph.facebook.com//v3.1/";


class Account{
    constructor(name){
        this.name = name;

    }
}

class InstagramAccount extends Account{
   async getAccountDetails(EdgeID, token){
        this.EdgeID = EdgeID;
        this.token = "&access_token=" + token;
        this.command = this.EdgeID+"?fields=name,username,website,biography,followers_count,follows_count,media_count,profile_picture_url"+this.token;
        this.details =  await this.getOpengraphResponse(this.command);
        console.log(this.details);
    }


    getOpengraphResponse(command){

      request.get({
        url: openGraphBaseURL+command,
        json: true,
        headers: {'User-Agent': 'request'}
      }, (err, res, data) => {
        if (err) {
          console.log('Error: ', err);
        }else if (res.statusCode !== 200) {
          console.log('Status:', res.statusCode);
        } else {

          console.log('getOpengraphResponse is ok');
          return data;
              }

      });
    }
}

getAccountDetails doesn't return anything, so does getOpengraphResponse — tkausl
– tkausl, Commented Aug 27, 2018 at 18:21
You aren't using Async/Await. You are using promises and they aren't fully implemented. — Adam H
– Adam H, Commented Aug 27, 2018 at 18:21
"request is 'request-promise-native'." - then why are you passing a callback to it when you say that it uses promises? — Bergi
– Bergi, Commented Aug 27, 2018 at 18:23
@AdamH What do you mean by "They aren't fully implemented"? — Bergi
– Bergi, Commented Aug 27, 2018 at 18:26
@Bergi Meaning that there is no implementation for .then, .error and nothing is being done with the result. — Adam H
– Adam H, Commented Aug 27, 2018 at 18:27

mehta-rohan · Accepted Answer · 2018-08-28 10:02:05Z

3

async/await can implemented with promises. i.e

var function_name = function(){
    // Create a instance of promise and return it.
    return new Promise(function(resolve,reject){ 
         // this part enclose some long processing tasks
         //if reject() or resolve()
         //else reject() or resolve() 
    });
}


//function which contains await must started with async
async function(){ 
     // you need to enclose the await in try/catch if you have reject statement  
     try{
         await function_name(); // resolve() is handled here.
         console.log('this will execute only after resolve statement execution');         
     }catch(err){
          // reject() is handled here.         
           console.log('this will execute only after reject statement execution'); 
     }
}

You can also use then/catch instead of try/catch.

edited Aug 28, 2018 at 10:02

answered Aug 27, 2018 at 18:56

mehta-rohan

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2 Comments

Tobi Over a year ago

Thank you. With a new Promise Object it works. But i thought 'request-promise-native' returns an own Promise.

mehta-rohan Over a year ago

sorry for my mistake. but the whole idea is about promise

Quentin · Accepted Answer · 2018-08-27 18:25:33Z

1

You can only (usefully) await a promise.

getOpengraphResponse doesn't return a promise. It has no return statement at all, so it returns undefined.

You'll need to treat the return value of request.get as a promise. Don't pass it a callback. Do use then or await.

Return either the value you want (if you await inside getOpengraphResponse) or the return value of request.get.

edited Aug 27, 2018 at 18:25

answered Aug 27, 2018 at 18:21

Quentin

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2 Comments

tadman Over a year ago

You can await something that returns undefined but don't expect it to do anything useful.

Bergi Over a year ago

(request-promise-native already returns a promise, there's no need to wrap it, one just has to use it correctly)

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