Intro to Mongoose Reading with a Model

Learning objective: By the end of this lesson, students will understand how to read documents from MongoDB using the find(), findById(), and findOne() methods in Mongoose.

Mongoose offers several methods for retrieving documents from a MongoDB database. Depending on the requirement, you can fetch a single document, multiple documents, or documents that match certain criteria.

The find() method

The find() method is used to retrieve all documents (or all documents that meet certain criteria) from a collection.

Let’s take a look at an example:

const todos = await Todo.find({});

The find() method accepts a query object and returns an array of documents from the relevant collection. The query object can outline the search criteria for the documents we wish to return. An empty object ({}) indicates that there are no search criteria, and all documents in the Todo collection should be retrieved.

💡 The find() method will always return an array, even if the array only includes a single result.

The findById() method

The findById() method is used to fetch a single document based on its unique _id.

Let’s take a look at an example:

const id = "657743d4c3b284c0ef6fd001";
const todo = await Todo.findById(id);

The findById method accepts an ObjectId and retrieves the document with that unique identifier from the collection. If a string value is passed in, Mongoose will automatically convert it into a MongoDB ObjectId.

The findOne() method

The findOne() method is useful for finding the first document that matches the given criteria.

Let’s take a look at an example:

const todo = await Todo.findOne({ text: "Learn JS" });

The findOne() method accepts a query object that specifies the criteria by which to find the document. In the example above, the method will return the first Todo document with a text value of Learn JS.

Reading many todos

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

Build the findTodos function

First let’s build out a function that retrieves a list of todos:

// queries.js

const findTodos = async () => {
  const todos = await Todo.find({});
  console.log("All todos:", todos);
};

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

// queries.js

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

If you haven’t done so already, be sure to remove or comment out createTodo() from our last example

Run the findTodos function

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

node queries.js

Check your terminal for the following output:

All todos: [
  {
    _id: new ObjectId('6573745144784f6dc034e1df'),
    text: 'Learn JS',
    isComplete: false,
    __v: 0
  },
  {
    _id: new ObjectId('6573745bfb58313f9376efe5'),
    text: 'Learn HTML',
    isComplete: false,
    __v: 0
  },
  {
    _id: new ObjectId('6573746529759ca5e8f2779b'),
    text: 'Learn CSS',
    isComplete: false,
    __v: 0
  }
]