Update Array element in MongoDB?

Use $addToSet operator to update array element. Let us first create a collection with documents −

> db.updateArrayDemo.insertOne(
...    {
...
...       "ClientDetails" : [
...          {
...             "ClientName" : "John",
...             "DeveloperDetails" : [ ]
...          },
...          {
...             "ClientName" : "Larry",
...             "DeveloperDetails" : [ ]
...          }
...       ]
...    }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5ccf465edceb9a92e6aa1960")
}

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

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

This will produce the following output −

{
   "_id" : ObjectId("5ccf465edceb9a92e6aa1960"),
   "ClientDetails" : [
      {
         "ClientName" : "John",
         "DeveloperDetails" : [ ]
      },
      {
         "ClientName" : "Larry",
         "DeveloperDetails" : [ ]
      }
   ]
}

Following is the query to update array element −

> db.updateArrayDemo.update({ "ClientDetails.ClientName": "Larry" },
{ $addToSet: { "ClientDetails.$.Technology": { 'DeveloperName': "Chris", 'WorkExperience':5 } } }, false, true);
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Let us check the array element has been updated or not −

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

This will produce the following output −

{
   "_id" : ObjectId("5ccf465edceb9a92e6aa1960"),
   "ClientDetails" : [
      {
         "ClientName" : "John",
         "DeveloperDetails" : [ ]
      },
      {
         "ClientName" : "Larry",
         "DeveloperDetails" : [ ],
         "Technology" : [
            {
               "DeveloperName" : "Chris",
               "WorkExperience" : 5
            }
         ]
      }
   ]
}