Styjun

I'm writing a REST API in Node.js using Mongoose to access the MongoDB backend database. I want to provide an API endpoint that returns a count of the number of array objects that match a particular variationStatus.

This is what I have so far but it gives me an empty response...

//Get 'Approved' count
app.get("/v1/approvedcount", async (request, response) => 
 var status = 'Approved';
 try 
 var result = await variationsModel.find( 'variations.variationStatus': status ).exec().count();
 response.send(result);
 catch (error) 
 response.status(500).send(error);
 
 )

And this is my model...

const variationsModel = mongoose.model("variations", 
 "variations": [
 
 "variationID": String,
 "custID": String,
 "projID": String,
 "variationTitle": String,
 "variationDesc": String,
 "variationStatus": String,
 "variationChargeable": String,
 "variationCost": String,
 "requireMaterial": String,
 "variationRequestor": String,
 "variationCreationDate": String,
 "variationImages": [
 
 "imageId": String
 
 ],
 "variationCategory": String
 
 ]
);

Anyone help me out?

Thanks!

You can use MongoDB aggregation pipeline to achieve the same.

Try this:

variationsModel
 .aggregate([
 $match : 
 'variations.variationStatus' : status
 
 ,
 $unwind : "variations"
 ,
 $match : 
 'variations.variationStatus' : status
 
 ,
 $group : 
 _id : "$_id",
 variations : 
 $push : '$variations'
 
 
 ,
 $project : 
 count : $size : $variations
 
 ]);

Explanation:

1. $match : To only select those documents which have atleast one element in variations array with variationStatus : status




2. $unwind : To expand the variations array and convert it from array to object. $unwind creates multiple documents from single document, with individual array elements, and all the other field remains same.




3. $match : To select only those documents which has variations.variationStatus:status




4. $group : Group all the documents back into original form (group with _id), and create variations array again, but this time it will only contain those elements with variationStatus :status




5. $project : This step is specifically to count the size of variations array , using $size.

For detailed info, please read MongoDb $unwind , $project and $size documentation.