Update Document

To update an existing document we can use the updateOne() or updateMany() methods.

The first parameter is a query object to define which document or documents should be updated.

The second parameter is an object defining the updated data.

updateOne()

The updateOne() method will update the first document that is found matching the provided query.

Let's see what the "like" count for the post with the title of "Post Title 1":

db.posts.find( { title: "Post Title 1" } ) 

Now let's update the "likes" on this post to 2. To do this, we need to use the $set operator.

db.posts.updateOne( { title: "Post Title 1" }, { $set: { likes: 2 } } ) 

Check the document again and you'll see that the "like" have been updated.

db.posts.find( { title: "Post Title 1" } ) 

Insert if not found

If you would like to insert the document if it is not found, you can use the upsert option.

db.posts.updateOne( 
  { title: "Post Title 5" }, 
  {
    $set: 
      {
        title: "Post Title 5",
        body: "Body of post.",
        category: "Event",
        likes: 5,
        tags: ["news", "events"],
        date: Date()
      }
  }, 
  { upsert: true }
)

updateMany()

The updateMany() method will update all documents that match the provided query.

db.posts.updateMany({}, { $inc: { likes: 1 } })

Now check the likes in all of the documents and you will see that they have all been incremented by 1.