Working with nested await in javascript

Question

I am implementing cache using MongoDB in-memory and MongoDB database in Nodejs application using mongoose. Here Nodejs 8.9 is used with async/await support.

let get_func = async(userId) => {

    let is_cached = await cache_user.findOne({ user_id: userId });

    if(!is_cached){
        console.log("NOT CACHIED");
        let is_dbuser = await db_user.find({});
        console.log(is_dbuser);

    } else {
        console.log("CACHED");
    }

    console.log("LEAVING get_func")
};

get_func(100);

And here's the output:

NOT CACHIED
[]
LEAVING get_func

However db_user is filled with data and was able to verify using:

db_user.find({}, function(err, users) {
   if (err) throw err;
   console.log(users);
});

Moreover checked with let is_error, is_dbuser = await db_user.find({}); if there's a doubt that function returns error and results in that order.

What's the way I should handle this nested await statement. (However it seems function is waiting for second await as expected).

let is_error, is_dbuser = await db_user.find({}); wont work. If the promise is rejected, await will behave like throw — Jonas Wilms
– Jonas Wilms, Commented Nov 13, 2017 at 16:27
Yeah seems to return promise. Works fine with you other moongose query. Problem only with inner wait. — udarabibile
– udarabibile, Commented Nov 13, 2017 at 16:35
I seem to remember that in order to get a fully-fledged promise in Mongoose you need exec(). Have you tried: b_user.find({}).exec()? — Mark
– Mark, Commented Nov 13, 2017 at 16:38

Jalasem · Accepted Answer · 2017-11-13 22:02:13Z

1

do this instead

let get_func = async (userId) => {

    let is_cached = await cache_user.findById(userId);

    if(!is_cached){
        console.log("NOT CACHIED");
        let is_dbuser = await db_user.find({});
        console.log(is_dbuser);

    } else {
        console.log("CACHED");
    }

    console.log("LEAVING get_func")
};

get_func(100);

please take note that it makes more sense to use findById unless it doesn't satisfy your query requirements and also async may require space before the parenthesis

answered Nov 13, 2017 at 22:02

Jalasem

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