Search Array for Values and Output Indexes in MongoDB

For this, use $indexOfArray. Let us first create a collection with documents −

> db.demo381.insertOne({"Values":[10,40,60,30,60]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e5b59f72ae06a1609a00b15")
}
> db.demo381.insertOne({"Values":[100,500,700,500,800]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e5b59f72ae06a1609a00b16")
}
> db.demo381.insertOne({"Values":[20,40,30,10,60]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e5b59f72ae06a1609a00b17")
}

Display all documents from a collection with the help of find() method −

> db.demo381.find();

This will produce the following output −

{ "_id" : ObjectId("5e5b59f72ae06a1609a00b15"), "Values" : [ 10, 40, 60, 30, 60 ] }
{ "_id" : ObjectId("5e5b59f72ae06a1609a00b16"), "Values" : [ 100, 500, 700, 500, 800 ] }
{ "_id" : ObjectId("5e5b59f72ae06a1609a00b17"), "Values" : [ 20, 40, 30, 10, 60 ] }

Following is the query to search an array for values present in another array and output the indexes of values found into a new array in MongoDB −

> db.demo381.aggregate([
...    {"$project":{
...       "Result":{
...          "$map":{
...             "input":[10,40],
...             "in":{"$indexOfArray":["$Values","$$this"]}
...          }
...       }
...    }}
... ])

This will produce the following output −

{ "_id" : ObjectId("5e5b59f72ae06a1609a00b15"), "Result" : [ 0, 1 ] }
{ "_id" : ObjectId("5e5b59f72ae06a1609a00b16"), "Result" : [ -1, -1 ] }
{ "_id" : ObjectId("5e5b59f72ae06a1609a00b17"), "Result" : [ 3, 1 ] }