Question

95

Requiring an async function in NodeJS

rated 0 times [ 101] [ 6] / answers: 1 / hits: 22019 / 7 Years ago, wed, july 12, 2017, 12:00:00

I am trying to get my head around async/await in NodeJS.

I have a function in a file as follows:

const getAccessToken = async () => {

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



    const oauthOptions = {

      method: 'POST',

      url: oauthUrl,

      headers: {

        'Authorization': 'Basic ' + oauthToken

      },

      form: {

        grant_type: 'client_credentials'

      }

    };



    request(oauthOptions)

      .then((err, httpResponse, body) => {

        if (err) {

          return reject('ERROR : ' + err);

        }

        return resolve(body.access_token);

      })

      .catch((e) => {

        reject('getAccessToken ERROR : ' + e);

      });

  });

};



module.exports = getAccessToken;

This file is saved as twitter.js in a lib folder

In my index.js file I have the following:

const getAccessToken = require('./lib/twitter');



let accessToken;



try {

  accessToken = await getAccessToken();

} catch (e) {

  return console.log(e);

}



console.log(accessToken);

I get an error trying to run this code saying:

>   accessKey = await getAccessToken();

>                     ^^^^^^^^^^^^^^

> 

> SyntaxError: Unexpected identifier

>     at createScript (vm.js:74:10)

>     at Object.runInThisContext (vm.js:116:10)

>     at Module._compile (module.js:533:28)

>     at Object.Module._extensions..js (module.js:580:10)

>     at Module.load (module.js:503:32)

>     at tryModuleLoad (module.js:466:12)

>     at Function.Module._load (module.js:458:3)

>     at Function.Module.runMain (module.js:605:10)

>     at startup (bootstrap_node.js:158:16)

>     at bootstrap_node.js:575:3

Can I not await the required function as it is marked async ?

Answers

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zoiel

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2 Years ago

answered 7 Years ago marib · Accepted Answer

Your code is already correct. Without changing anything in twitter.js you have two options to use it:

Functions marked with async always return promises. Therefore you can simply do:

const getAccessToken = require('./lib/twitter');



getAccessToken().then(accessToken => {

    console.log(accessToken);

})

All functions that return promises can be awaited upon but you cannot use await outside of an async marked functions. So you can also do:

const getAccessToken = require('./lib/twitter');



(async function () {

    var accessToken = await getAccessToken();

    console.log(accessToken);

})();

The async/await keywords does not change how async functions behave. You still cannot wait on async functions synchronously, you can only do that inside an asynchronous function. Async/await is just a syntax sugar on top of promises.