Intro to Mongoose Updating with a Model

Learning objective: By the end of this lesson, students will understand how to update resources in a MongoDB database the save() and findByIdAndUpdate() methods in Mongoose.

Updating a document involves modifying its existing data while maintaining data integrity. Mongoose provides several methods for updating documents, each suitable for different scenarios.

Updating retrieved documents

One common approach to updating a document is to first retrieve the document, and then apply the necessary changes. This can be useful when you need to check the authorship of a resource before performing an operation.

The approach involves two steps:

1. Retrieve the document: Use the findById() method to fetch the document you want to update.
2. Apply the changes and save: Modify the document’s properties as needed and then save the changes using the save() method.

Let’s take a look at an example:

const id = '6573745144784f6dc034e1df';
const todo = await Todo.findById(id);
todo.isComplete = true;
await todo.save();

After retrieving the todo document, we update the isComplete property in the same way we would modify any regular JavaScript object property. Once this modification is made, the save() method is called on the todo instance to persist the changes to the database.

📚 The save() method is available on a Mongoose document instance (a retrieved document). When called on a document instance, it either inserts or updates the document in the database.

Simultaneous retrieval and update

Another approach to updating documents is using the findByIdAndUpdate() method. This method allows you to find a document by its _id and update it. It has the advantage of completing an update with a single operation.

The findByIdAndUpdate() method accepts 3 arguments and returns a single document:

1. ObjectId: The unique identifier (_id) of the document you want to update.
2. Update object: An object that specifies the changes to apply to the document.
3. Options object: An optional object used to specify various settings for the operation.

Let’s take a look at an example:

const id = '6573745144784f6dc034e1df';
const updatedTodo = await Todo.findByIdAndUpdate(
  id,
  { isComplete: true },
  { new: true }
);

In this example, we are finding a specific document with the value of the id variable. The second argument is our update object, which sets the document’s isComplete property to true. The third argument is an options object { new: true }, specifying that the modified document should be returned, not the original.

Implementing findByIdAndUpdate()

Let’s test some of these examples in our queries.js file.

Build an updateTodo function

First let’s build out a function for updating our todo:

// queries.js

const updateTodo = async () => {
  const id = '6573745144784f6dc034e1df';
  const updatedTodo = await Todo.findByIdAndUpdate(
    id,
    { isComplete: true },
    { new: true }
  );
  console.log("Updated todo:", updatedTodo);
};

Next, we’ll call updateTodo within the runQueries function:

// queries.js

const runQueries = async () => {
  console.log('Queries running.');
  await updateTodo();
};

If you haven’t done so already, be sure to remove or comment out any previous methods being called here

Run the updateTodo function

To execute the updateTodo function, run the queries.js file with the following command:

node queries.js

Check your terminal for the following output:

Updated todo: {
  _id: new ObjectId('6573745144784f6dc034e1df'),
  text: 'Learn JS',
  isComplete: true,
  __v: 0
}