await doesn't wait for function to end

Question

I know this has been asked a lot but I can't seem to use the existing answers to get my code to work. I am trying to use mongojs to make a single query, then put the results in a global (relative to the scope) variable to avoid nesting multiple callbacks. However, I can't seem to get the code to wait for the query to end before continuing.

async function taskmaster() {

    const db = mongojs(mongoUri.tasker);
    let currentDoc;
    
    const getTask = async function() { 
        db.tasks.findOne({'task_id': {'$in': [taskId, null]}}, function(err, doc) {
            console.log(doc);
            currentDoc = doc;
        });
    }

    await getTask();
    console.log(currentDoc);

    // Code to process currentDoc below
}

No matter what I do, console.log(doc) shows a valid MongoDB document, yet console.log(currentDoc) shows "undefined". Thanks in advance!

Answer 1

Inside your async function, you use findOne method() in callback style, so it's totally normal that console.log(currentDoc) shows undefined, because it executes before currentDoc = doc;

You can promisify the findOne method, to use it with async/await keyword.

I found a tutorial to promisfy a callback style function here, hope it help : https://flaviocopes.com/node-promisify/

--- EDIT ---

I rewrite your code when promising the findOne method, as suggested by O.Jones

async function taskmaster() {

    const getTask = async (taskId) => {
        return new Promise((resolve, reject) => {
           db.tasks.findOne({'task_id': {'$in': [taskId, null]}}, function(err, doc) {
              if(err) {
                  console.log("problem when retrieve data");
                  reject(err);
              } else {
                  resolve(doc);
              }
        });
    })
    
    const db = mongojs(mongoUri.tasker);
     
    const currentDoc = await getTask(taskId);
    console.log(currentDoc);
}