remove a property from an object in an array of objects mongoose

Question

I have a MongoDB document like this:

{
  "_id": ObjectId("5589044a7019e802d3e9dbc5"),
  groups:[
    {
      _id: 5a3326d01b2213894672fdd0,
      group_id: '13239517',
      thread_id: 'f32940da-12-15-01-9325790',
      Last_post_id: '981206845'
    }
  ]
}

I've tried a variation of $set and $unset using:

User.findOneAndUpdate({userId}, {groups:{$set: {thread_id: ''}}}, {new: true})

when I tried multiple variations of the above code I keep on getting groups where the affected object is only left with an id.

[
  { _id: 5a3326d41b2213894672fdd1 },
  {
    _id: 5a332a81479a728ebe4226e5,
    group_id: '13239517',
    thread_id: 'f32940da-12-15-01-9325790',
    Last_post_id: '981206845'
  }
]

I've also tried looping over the array of groups removing the key using reduce then just trying to set the groups to this new values like and that didn't work either.

let groups = groups.reduce((prev, ele)=>{
  // group_id is passed in as an argument
  if(ele.group_id === group_id){
    let chatThread = ele.thread_id
    delete ele.thread_id
    console.log(ele)
    return chatThread
  } else {
    return prev
  }
}, false)
User.findOneAndUpdate({userId}, {groups}, {new: true})

this just doesn't do anything.

My intended result would be where thread_id is gone

groups:[
  {
    _id: 5a3326d01b2213894672fdd0,
    group_id: '13239517',
    Last_post_id: '981206845'
  }
]

Although similar to link1 and link2 both of those solutions either don't change anything when saved or remove all properties other than _id.

Possible duplicate of Remove a field from array element in mongodb — s7vr
– s7vr, Commented Dec 15, 2017 at 2:43
As this is a duplicate, have a look at: stackoverflow.com/questions/19945924/… — rieckpil
– rieckpil, Commented Dec 15, 2017 at 4:23
@Veeram I tried those and it did not work for me it would either remove all properties except _id or do nothing at all. I did find a solution though based on those links so thank you very much. User.findOne({userId}, async(err, user)=>{ let newGroups = user.groups.map(ele=>{ if(ele.group_id === group_id){ return {group_id:ele.group_id,_id: ele._id,Last_post_id: ele.Last_post_id} }return ele })var updateUserGroups = await User.findOneAndUpdate({userId}, {groups: newGroups}, {new: true}) }) — Joshua Fermin
– Joshua Fermin, Commented Dec 15, 2017 at 15:53

Joshua Fermin · Accepted Answer · 2017-12-15 16:01:04Z

0

this did work for me. looks like reduce and map when using delete keyword will not affect the original array I assumed it would since i thought it was passed by reference.

User.findOne({userId}, async(err, user)=>{
            let new_groups = user.groups.map(ele=>{
              // group id is passed as an argument
              if(ele.group_id === group_id){
                return {
                  group_id:ele.group_id,
                  _id: ele._id,
                  Last_post_id: ele.Last_post_id
                }
              }
              return ele
            })
            var updateUserGroups = await User.findOneAndUpdate({userId}, {groups: new_groups}, {new: true})

answered Dec 15, 2017 at 16:01

Joshua Fermin

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1 Comment

s7vr Over a year ago

You can use User.update( {userId}, {$unset: {"groups.$[].thread_id":""}} ) in 3.6 to remove all the thread_ids from group array.

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