Populate an array with multiple mongo queries [duplicate]

Question

I'm having a problem with a callback mess.

In my nodejs app, I'm trying to get an array of JSON Objects returned by a mongoDB request. I don't know why, but it don't populate as I want.

I suspect a problem of asynchronous results/callback mess.

var fruits = ["Peach", "Banana", "Strawberry"];
var finalTab = [];
fruits.forEach(function(fruit) {
    db.collection('mycollection').distinct("column1", {"column2":{$regex :fruit}}, (function(err, result) {                 
        finalTab[fruit] = result;
        console.log(result); // -> display the desired content
        db.close();
        if (err) throw err;
    }));
});
console.log(finalTab); // -> []

Thanks by advance for help.

EDIT : As I need all results returned by my db.collection...functions... I'm trying to add these async commands to a queue, execute it and get a callback function. I think that async nodejs module can help.

Can someone tell me how to do this in a ForEach() ?

Finally got the right way to do it here : stackoverflow.com/a/48902134/5119290 — Adrien Tanaka
– Adrien Tanaka, Commented Feb 21, 2018 at 14:13

Rishikesh Dhokare · Accepted Answer · 2018-02-20 16:17:11Z

0

The line finalTab[fruit] = result; will not help because fruit there is not index. You need to use index in forEach() as follows -

var fruits = ["Peach", "Banana", "Strawberry"];
var finalTab = [];
fruits.forEach(function(fruit, index) {
    db.collection('mycollection').distinct("column1", {"column2":{$regex :fruit}}, (function(err, result) {                 
        finalTab[index] = result;
        console.log(result); // -> display the desired content
        db.close();
        if (err) throw err;
    }));
});
console.log(finalTab); // -> []

answered Feb 20, 2018 at 16:17

Rishikesh Dhokare

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4 Comments

Patrick Roberts Over a year ago

While this is a baby step in the right direction, there are still multiple problems with your code.

Adrien Tanaka Over a year ago

Is it possible to use the content of the fruit variable as a key of the array ? Like this -> [ 'Peach' => {myobject}, 'Banana' => ....etc ]

Adrien Tanaka Over a year ago

I edited my question Patrick. Can you help ?

Adrien Tanaka Over a year ago

Response here : stackoverflow.com/a/48902134/5119290

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