how to use .populate() in javascript-CodePudding

I have a collection called

CR

what I want to do is query CR like so:

let cre = await CR.find({myid: "xxxxxx"})

and i also have a collection called cla, but that one i need to query based off of the results of cre. The results of cre will return a class_id, in which I need to use to query the cla collection to find the _id. At the end of all of this, I want to ideally merge the two, which I believe you can do through .populate(), and then send it to teh front-end as one.;

I have tried this:

 let cre = await cr.find({myid: "xxx"}).populate('loc').populate('desc').populate('dt');

but this isn't working. how can I fix this?

CodePudding user response：

It may be due to schemas, but this is how it's clean and simple to use;

 let cre = await cr.find({myid: "xxx"}).populate(['loc','desc','dt']);

CodePudding user response：

Firstly, you can take cla collection "_id" in CR collection schema. In schema of CR collection refer to cla model id like this,

const creSchema = mongoose.Schema({
    name: String,
    classnId: { type: mongoose.Types.ObjectId, ref: "Cla" }
});

Then you can populate like,

const cres = await CR.find({}).populate({path:'classnId', select:'columnName'});

Hopefully, this will solve your issue.

Note: There in populating you can give multiple column names by space and if you give a minus before a column name like this (-columnName) then that column will not show when you will call the API.