How to pull even numbers from an array in MongoDB?

Use $mod to get the even numbers and pull them from the array. Let us first create a collection with documents −

>db.pullEvenNumbersDemo.insertOne({"AllNumbers":[101,102,104,106,108,109,110,112,14,17,18,21]});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd45b072cba06f46efe9eea")
}

Following is the query to display all documents from the collection with the help of find() method −

> db.pullEvenNumbersDemo.find().pretty();

This will produce the following output −

{
   "AllNumbers" : [
      102,
      104,
      106,
      108,
      109,
      110,
      112,
      14,
      17,
      18,
      21
   ]
}

Following is the query to pull even numbers from an array in MongoDB −

> db.pullEvenNumbersDemo.updateMany({},{ "$pull": { "AllNumbers": { "$mod": [ 2, 0 ] } } } );
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }

Let us check all the documents once again −

> db.pullEvenNumbersDemo.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5cd45b072cba06f46efe9eea"),
   "AllNumbers" : [
      101,
      109,
      17,
      21
   ]
}