How do I return data from a function in Node that connects to Mongodb? [duplicate]

Question

function getEmployees(jobID){
    MongoClient.connect(url, function(err, db){
        if(err) throw err;
        var dbo = db.db("mydb");
        dbo.collection("employees").find({employee:jobID}).toArray(function(err, result){
            if(err) throw err;
            db.close();
            console.log(result) // shows the employees. cool!
            // how do I return result??
        })
    })
}
var employees = getEmpoyees(12345);  // I want the employees variable to be an array of employees

I'm new to node.js and javascript and I can't figure this out. Do I need to implement a callback to use the data the way I'm trying to?

Can you share all your code? Have you installed and imported mongoose ? — Chef1075
– Chef1075, Commented Jan 12, 2018 at 23:22
You won't be able to get the value in that way. Have you used promises before? — Alberto Rivera
– Alberto Rivera, Commented Jan 12, 2018 at 23:24
”Do I need to implement a callback to use the data the way I’m trying to?” - yes, or better still go learn about Promises (MongoDB uses them out the box). Promises work particularly well with async / await. — James
– James, Commented Jan 12, 2018 at 23:25

Mikhail Zharnikov · Accepted Answer · 2018-01-12 23:38:24Z

4

Very interesting question. In this case, you can't return value directly. So I implemented indirect way to get the return value. For this, I added "callback" function as the function parameter in "getEmployees" function. The updated code is as follows.

function getEmployees(jobID, callBack){
MongoClient.connect(url, function(err, db){
    if(err) throw err;
    var dbo = db.db("mydb");
    dbo.collection("employees").find({employee:jobID}).toArray(function(err, result){
        if(err) throw err;
        db.close();
        console.log(result) // shows the employees. cool!
        // you can return result using callback parameter
        return callBack(result);
    })
})
}
var employees = getEmpoyees(12345, function(result) {
   console.log(result);
});  // I want the employees variable to be an array of employees

answered Jan 12, 2018 at 23:38

Mikhail Zharnikov

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5 Comments

James Over a year ago

”very interesting question” - I think you’re confusing “interesting” with “common”.

maggotbrain Over a year ago

this worked! thanks.

maggotbrain Over a year ago

actually, console.log(result) outputs the result but the employees variable is still undefined :(

Mikhail Zharnikov Over a year ago

The only case the result is undefined is that the function is finished before "return" query. So I think database error is occured before callBack.

Mikhail Zharnikov Over a year ago

The only case the result is undefined is that the function is finished before 'return' query. I think database error is occurred so callBack didn't run. If my answer is correct, will you vote it?

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