Awaiting functions in parameter-CodePudding

I want to await the function call which is passed in the parameter from the in-built google API call and return the results after it parameter function is executed. But I'm not able to get on with it.

async function list(auth, userId) {
    const gmail = google.gmail({ version: 'v1', auth });
    const result;
    await gmail.users.messages.list({
        userId: userId,
    }, async (err, res) => {
        if (err) return console.log('The API returned an error: '   err);
        console.log(res.data);
        result = await res.data;  // I want to await this part
    });

    return result;
}
...

const returnedResult = await list(auth, id);
console.log(returnedResult);

What happens in the above code is that 'result' and 'returnResult' remain undefined and are output first and then res.data is logged into the console. Any help would be appreciated. Thanks in advance

CodePudding user response：

With regards to the following:

result = await res.data; // I want to await this part

Awaiting on a non-promise value wouldn't help solving your problem. Assuming gmail.users.messages.list(...) returns a promise, instead of setting the result in the onFulfilled function, try this:

async function list(auth, userId) {
  // ...

  let result;
  try {
    result = await gmail.users.messages.list({ userId: userId });
  } catch (ex) {
    console.error('The API returned an error', ex)
  }

  return result;
}

CodePudding user response：

Though it's not the exact answer of how to await the functions in parameter, but the workaround such cases. In my case replacing

await gmail.users.messages.list({...}, (err, res) => {...});

with

try{
   const res = await gmail.users.messages.list({user: userId});
   console.log(res.data);
   return res.data
} catch(err) {
   return console.log('The API returned an error: '   err);
}