Conditional check inside nested array in MongoDb - mongodb

Question

After a few pipeline stages, I came up with following sample result which is one document. If the videos.views.userId contains 10, I need to indicate videos.isWatched = true else false. We can use $unwind, check the condition, then group it.
This is sample output, The original document contains a lot of field, so I just like to do with less code unless I need to unwind Is there any way to do without unwind("videos")?
[
{
"_id":"someId",
"videos":[
{
"_id":"1",
"name":"A",
"views":[
{
"userId":10,
"group":"X"
}
]
},
{
"_id":"2",
"name":"B",
"views":[
{
"userId":20,
"group":"Y"
}
]
}
],
"Assessment":[
{
"_id":"22",
"title": "Hello world"
}
]
}
]
Expected result
[
{
"_id":"someId",
"videos":[
{
_id:"1",
name:"A",
views:[
{
userId:10,
group:"X"
}
],
"isWatched":true
},
{
_id:"2",
name:"B",
views:[
{
userId:20,
group:"Y"
}
],
"isWatched":false
}
],
"Assessment":[
{
_id:"22",
title: "Hello world"
}
]
}
]

Answer 1

You can use $map along with $mergeObjects to add a new field to an existing array. $anyElementTrue can be used to determine whether there's any userId equal to 10:
db.collection.aggregate([
{
$addFields: {
videos: {
$map: {
input: "$videos",
in: {
$mergeObjects: [
"$$this",
{
isWatched: {
$anyElementTrue: {
$map: { input: "$$this.views", in: { $eq: [ "$$this.userId", 10 ] } }
}
}
}
]
}
}
}
}
}
])
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