CODEWITHSUNDEEP
arraysmongodbaggregation-framework
Robert O'Brien
Robert O'Brien

Reputation: 183

Performing 2 seperate .map operations on a mongo query stored in a variable

I have this query stored in a variable as follows

var recent_Polls = db.Trump_Vs_Biden_V1.aggregate(
  [
    { $match : {"State":state_Val}},
    {$sort:{"Date":-1}},
    {$limit: 5 }
  ]
)

and it returns these 5 documents

Link to documents returned

As u can see in each document there is

"Biden" : 59, "Trump" : 32

I wish to get all of the Biden values into one array and all the trump values into a seperate array so i can perform mathematical operations on them.

So for example this is the desired output i would like for all the trump values..

[
36,
32,
32,
31,
36
 ]

and vice versa for biden...

in order to do this i attempted using the .map function.

var trump_Nums = recent_Polls.map(function(e2){return e2.Trump})

And this worked but when i tried to perform the exact same operation on the biden values

recent_Polls.map(function(e2){return e2.Biden})

i got an empty array in return..

I was wondering if anybody could think of a fix to this were i could retrieve both the trump and biden values all at once into 2 seperate arrays. That is maybe more efficient..

Upvotes: 0

Views: 25

Answers (1)

Joe
Joe

Reputation: 28326

To get this on the client side, you might try forEach:

var trump_Nums = [];
var biden_Nums = [];
recent_Polls.forEach(function(e2){
                          trump_Nums.push(e2.Trump);
                          biden_Nums.push(e2.Biden)
});

To get this from the server, add a $group stage to the aggregation:

{$group: {
          _id:null,
          Biden:{$push: "$Biden"},
          Trump:{$push: "$Trump"}
}}

Playground

If you need the full documents at the same time as the numbers, add a $facet stage to your original aggregation:

{$facet: {
          documents:[{$match:{}}],
          numbers: [{$group: {
                              _id:null,
                              Biden:{$push: "$Biden"},
                              Trump:{$push: "$Trump"}
          }}]    
}}

Playground

Upvotes: 1

Related Questions