javascript - 尝试通过不同的功能使用Async和Await(Trying to use Async and Await from different functions)

Question

While I thought I was using Async and Await keywords properly, it appears as though I am doing something wrong.

(当我以为我正确使用了Async和Await关键字时，好像我做错了什么。)

I am using PouchDB, which is a great Javascript database that syncs with CouchDB.

(我正在使用PouchDB，这是一个与CouchDB同步的出色Javascript数据库。)

PouchDB uses promises for many of its functions, and has native support for Async and Await.

(PouchDB的许多功能都使用了promises，并且对Async和Await具有本机支持。)

As an example, to retrieve the basic information about a database, you would use the following code:

(例如，要检索有关数据库的基本信息，可以使用以下代码：)

    db.info().then(function (info) {
  console.log(info);
})

I understand this, and it works.

(我了解这一点，并且有效。)

But if I try and put this inside a function, and then call that function, things go haywire.

(但是，如果我尝试将其放在一个函数中，然后调用该函数，事情就会变得一团糟。)

And I'm sure it's me and not PouchDB that is the problem...

(而且我确定是问题所在，而不是PouchDB。)

function getLocalDBInfo(db){

  try {
    db.info().then(function (info) {
      return info;
    });
  } catch (error) {
    console.log("can't get local DB info: ", error);
  }
}

async function testing(db){
  try {
    var info=await getLocalDBInfo(db);
    await console.log("DB info=", info);
    await console.log("Doc count= ", info.doc_count);
  }
  catch(err){
    console.log("error=",err);
  }

  //info contains...
    //{"doc_count":0,"update_seq":0,"db_name":"kittens"}
}

testing(MY_db);

If I log info inside the getLocalDBInfo function, it eventually (ie. after the promise fulfills) logs info to the console.

(如果我在getLocalDBInfo函数中记录info ，它最终（即在诺言履行后）会将info记录到控制台。)

But, the logs inside the testing function return immediately with undefined .

(但是， testing函数中的日志立即返回undefined 。)

It makes sense to me that they are returning undefined because they are returning immediately, but I was trying to have them wait for info by using async and await .

(对我来说，它们返回undefined是有道理的，因为它们会立即返回，但是我试图通过使用async和await来让它们等待info 。)

Any suggestions as to what I am doing wrong?

(关于我在做什么错的任何建议吗？)

  ask by robert smith translate from so

Answer 1

getLocalDBInfo() is not returning a promise, so you can't await for it.

(getLocalDBInfo（）没有返回承诺，因此您无法等待。)

with async/await you could:

(使用异步/等待，您可以：)

async function getLocalDBInfo(db){
    try{
       return await db.info()
    } catch (err){
       console.log("can't get local DB info: ", error);
    }
}

you can also use new promise

(您也可以使用新的承诺)