How to find Mongoose data recursively? - node.js

Question

I am newbie in MEANJS and i have a problem i.e, there are collection called employee and have multiple documents with their boss field. Now i want get all employees with their lower level.
For example:-
1) {_id:ObjectId('587dcd3edca5f235f862fdfd'), name:'John'} //he doesn't have boss
2) {_id:ObjectId('587dcd3edca5f235f86dddew'), name: 'Jimmy', 'boss': ObjectId('587dcd3edca5f235f862fdfd')} //john is boss
3) {_id:ObjectId('587dcd3edca5f235f863ew'), name: 'David', 'boss': ObjectId('587dcd3edca5f235f86dddew')} //john,Jimmy are bosses
4) {_id:ObjectId('587dcd3edca5f235f86qwa'), name: 'Dyan', 'boss': ObjectId('587dcd3edca5f235f86dddew')} //john,Jimmy,David are bosses
5) {_id:ObjectId('587dcd3edca5f235f8ew32'), name:'Jack', 'boss': ObjectId('587dcd3edca5f235f862fdfd')} //john is boss
6) {_id:ObjectId('587dcd3edca5f2wsw23rlot'), name: 'Loren', 'boss':ObjectId('587dcd3edca5f235f8ew32')} //john,Jack is boss
If we take
Jonh then output will ['Jimmy','Jack','David','Dyan','Loren']
Jack then output will ['Loren']
Here is my try code:-
getBosses(user._id)
function getBosses(id){
User.find({boss:id})
.exec(function(err,users){
if(err)
return console.log(err);
//How handle here 'users' array
//for something getBosses call recursively
})
}

Answer 1

As far as I understood you need to find all subordinates of that people. I think the best way to do it is using $graphLookup.
db.bosses.insertMany([
{ _id: "587dcd3edca5f235f862fdfd", name: "John" },
{
_id: "587dcd3edca5f235f86dddew",
name: "Jimmy",
boss: "587dcd3edca5f235f862fdfd",
},
{
_id: "587dcd3edca5f235f863ew",
name: "David",
boss: "587dcd3edca5f235f86dddew",
},
{
_id: "587dcd3edca5f235f86qwa",
name: "Dyan",
boss: "587dcd3edca5f235f86dddew",
},
{
_id: "587dcd3edca5f235f8ew32",
name: "Jack",
boss: "587dcd3edca5f235f862fdfd",
},
{
_id: "587dcd3edca5f2wsw23rlot",
name: "Loren",
boss: "587dcd3edca5f235f8ew32",
},
]);
db.bosses.aggregate([
{
$graphLookup: {
from: "bosses",
startWith: "$_id",
connectFromField: "_id",
connectToField: "boss",
as: "subordinates",
},
},
{
$project: {
_id: false,
name: true,
subordinates: {
$reduce: {
input: "$subordinates",
initialValue: "",
in: { $concat: ["$$value", ", ", "$$this.name"] },
},
},
},
},
{
$project: {
name: true,
subordinates: { $substrBytes: ["$subordinates", 2, -1] },
},
},
]);
The result of the last one is:
[
{ name: 'John', subordinates: 'David, Dyan, Loren, Jack, Jimmy' },
{ name: 'Jimmy', subordinates: 'David, Dyan' },
{ name: 'David', subordinates: '' },
{ name: 'Dyan', subordinates: '' },
{ name: 'Jack', subordinates: 'Loren' },
{ name: 'Loren', subordinates: '' }
]
The most important thing is $graphLookup stage of the aggregate pipeline. Last two $project stages is just response formatting - return only name and subordinates as string field with comma separated names.
To get data for a specific person you can use $match stage before $graphLookup like that:
db.bosses.aggregate([
{ $match: { name: "John" } },
{
$graphLookup: ...