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yiha
Asked: 2022-10-25 08:17:49 +0800 CST 2022-10-25 08:17:49 +0800 CST

I have two collections, old_user and new_user and I want to enter two fields in one of them with the values ​​they have in the other, but it gives me a null value

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I have tried to pass the entire collection, and if it saves the value, as an array (logical), but what I want is that it only saves the newField and secondField fields with their respective values ​​in the old_user collection of the new_user collection, but I save them as null, this is the code:

db.getCollection("old_user").find()
  .forEach((elm) => {

    let elmId = elm.id

    let new_user = db.getCollection("new_user").find( {id : elmId}).toArray()

      if(new_user) {
        db.getCollection("old_user").updateOne({id: elmId}, {$set: {newfield: new_user.newField, secondfield: new_user.secondField}})
      }
  })

As far as I know, to access an object inside an array it is with the point annotation, if I make a query of the entire collection it returns it to me but if I do a console.log of new_user.newField it returns it to me as null

I appreciate any help!

javascript

1 Answers

  1. Best Answer

    The problem is that you are usingfind

    let new_user = db.getCollection("new_user").find( {id : elmId}).toArray()

    And findit returns multiple elements. Therefore the property new_user.newFielddoes not exist.

    You must change it to findOne:

    let new_user = db.getCollection("new_user").findOne( {id : elmId}).toArray()
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