Node.js MongoDB

Node.js MongoDB

Node.js can be used in database applications.

One of the most popular NoSQL database is MongoDB.

MongoDB

To be able experiment with the code examples, you will need access to a MongoDB database.

You can download a free MongoDB database at https://www.mongodb.com.

Install MongoDB Driver

Let us try to access a MongDB database with Node.js.

To download and install the official MongoDB driver, open the Command Terminal and execute the following:

Download and install mongodb package:

C:\Users\Your Name>npm install mongodb

Now you have downloaded and installed a mongodb database driver.

Node.js can use this module to manipulate MongoDB databases:

var mongo = require('mongodb');

Node.js MongoDB Create Database

Creating a Database

To create a database in MongoDB, start by creating a MongoClient object, then specify a connection URL with the correct ip address and the name of the database you want to create.

MongoDB will create the database if it does not exist, and make a connection to it.

Example

Create a database called "mydb":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/mydb";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
console.log("Database created!");
db.close();
});

Save the code above in a file called "demo_create_mongo_db.js" and run the file:

Run "demo_create_mongo_db.js"

C:\Users\Your Name>node demo_create_mongo_db.js

Which will give you this result:

Database created!

Node.js MongoDB Create Collection

A collection in MongoDB is the same as a table in MySQL

Creating a Collection

To create a collection in MongoDB, use the createCollection() method:

Example

Create a collection called "customers":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.createCollection("customers", function(err, res) {
    if (err) throw err;
    console.log("Collection created!");
    db.close();
});
});

Save the code above in a file called "demo_mongodb_createcollection.js" and run the file:

Run "demo_mongodb_createcollection.js"

C:\Users\Your Name>node demo_mongodb_createcollection.js

Which will give you this result:

Collection created!

Node.js MongoDB Insert

Insert Into Collection

To insert a record, or document as it is called in MongoDB, into a collection, we use the insertOne() method.

A document in MongoDB is the same as a record in MySQL

The first parameter of the insertOne() method is an object containing the name(s) and value(s) of each field in the document you want to insert.

It also takes a callback function where you can work with any errors, or the result of the insertion:

Example

Insert a document in the "customers" collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myobj = { name: "Company Inc", address: "Highway 37" };
dbo.collection("customers").insertOne(myobj, function(err, res) {
    if (err) throw err;
    console.log("1 document inserted");
    db.close();
});
});

Save the code above in a file called "demo_mongodb_insert.js" and run the file:

Run "demo_mongodb_insert.js"

C:\Users\Your Name>node demo_mongodb_insert.js

Which will give you this result:

1 document inserted

Note: If you try to insert documents in a collection that do not exist, MongoDB will create the collection automatically.

Insert Multiple Documents

To insert multiple documents into a collection in MongoDB, we use the insertMany() method.

The first parameter of the insertMany() method is an array of objects, containing the data you want to insert.

It also takes a callback function where you can work with any errors, or the result of the insertion:

Example

Insert multiple documents in the "customers" collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myobj = [
    { name: 'John', address: 'Highway 71'},
    { name: 'Peter', address: 'Lowstreet 4'},
    { name: 'Amy', address: 'Apple st 652'},
    { name: 'Hannah', address: 'Mountain 21'},
    { name: 'Michael', address: 'Valley 345'},
    { name: 'Sandy', address: 'Ocean blvd 2'},
    { name: 'Betty', address: 'Green Grass 1'},
    { name: 'Richard', address: 'Sky st 331'},
    { name: 'Susan', address: 'One way 98'},
    { name: 'Vicky', address: 'Yellow Garden 2'},
    { name: 'Ben', address: 'Park Lane 38'},
    { name: 'William', address: 'Central st 954'},
    { name: 'Chuck', address: 'Main Road 989'},
    { name: 'Viola', address: 'Sideway 1633'}
];
dbo.collection("customers").insertMany(myobj, function(err, res) {
    if (err) throw err;
    console.log("Number of documents inserted: " + res.insertedCount);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_insert_multiple.js" and run the file:

Run "demo_mongodb_insert_multiple.js"

C:\Users\Your Name>node demo_mongodb_insert_multiple.js

Which will give you this result:

Number of documents inserted: 14

The Result Object

When executing the insertMany() method, a result object is returned.

The result object contains information about how the insertion affected the database.

The object returned from the example above looked like this:

{
result: { ok: 1, n: 14 },
ops: [
    { name: 'John', address: 'Highway 71', _id: 58fdbf5c0ef8a50b4cdd9a84 },
    { name: 'Peter', address: 'Lowstreet 4', _id: 58fdbf5c0ef8a50b4cdd9a85 },
    { name: 'Amy', address: 'Apple st 652', _id: 58fdbf5c0ef8a50b4cdd9a86 },
    { name: 'Hannah', address: 'Mountain 21', _id: 58fdbf5c0ef8a50b4cdd9a87 },
    { name: 'Michael', address: 'Valley 345', _id: 58fdbf5c0ef8a50b4cdd9a88 },
    { name: 'Sandy', address: 'Ocean blvd 2', _id: 58fdbf5c0ef8a50b4cdd9a89 },
    { name: 'Betty', address: 'Green Grass 1', _id: 58fdbf5c0ef8a50b4cdd9a8a },
    { name: 'Richard', address: 'Sky st 331', _id: 58fdbf5c0ef8a50b4cdd9a8b },
    { name: 'Susan', address: 'One way 98', _id: 58fdbf5c0ef8a50b4cdd9a8c },
    { name: 'Vicky', address: 'Yellow Garden 2', _id: 58fdbf5c0ef8a50b4cdd9a8d },
    { name: 'Ben', address: 'Park Lane 38', _id: 58fdbf5c0ef8a50b4cdd9a8e },
    { name: 'William', address: 'Central st 954', _id: 58fdbf5c0ef8a50b4cdd9a8f },
    { name: 'Chuck', address: 'Main Road 989', _id: 58fdbf5c0ef8a50b4cdd9a90 },
    { name: 'Viola', address: 'Sideway 1633', _id: 58fdbf5c0ef8a50b4cdd9a91 } ],
insertedCount: 14,
insertedIds: [
    58fdbf5c0ef8a50b4cdd9a84,
    58fdbf5c0ef8a50b4cdd9a85,
    58fdbf5c0ef8a50b4cdd9a86,
    58fdbf5c0ef8a50b4cdd9a87,
    58fdbf5c0ef8a50b4cdd9a88,
    58fdbf5c0ef8a50b4cdd9a89,
    58fdbf5c0ef8a50b4cdd9a8a,
    58fdbf5c0ef8a50b4cdd9a8b,
    58fdbf5c0ef8a50b4cdd9a8c,
    58fdbf5c0ef8a50b4cdd9a8d,
    58fdbf5c0ef8a50b4cdd9a8e,
    58fdbf5c0ef8a50b4cdd9a8f
    58fdbf5c0ef8a50b4cdd9a90,
    58fdbf5c0ef8a50b4cdd9a91 ]
}

The values of the properties can be displayed like this:

Example

Return the number of inserted documents:

console.log(res.insertedCount)

Which will produce this result:

14

The _id Field

If you do not specify an _id field, then MongoDB will add one for you and assign a unique id for each document.

In the example above no _id field was specified, and as you can see from the result object, MongoDB assigned a unique _id for each document.

If you do specify the _id field, the value must be unique for each document:

Example

Insert three records in a "products" table, with specified _id fields:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myobj = [
    { _id: 154, name: 'Chocolate Heaven'},
    { _id: 155, name: 'Tasty Lemon'},
    { _id: 156, name: 'Vanilla Dream'}
];
dbo.collection("products").insertMany(myobj, function(err, res) {
    if (err) throw err;
    console.log(res);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_insert_id.js" and run the file:

Run "demo_mongodb_insert_id.js"

C:\Users\Your Name>node demo_mongodb_insert_id.js

Which will give you this result:

{
result: { ok: 1, n: 3 },
ops: [
    { _id: 154, name: 'Chocolate Heaven },
    { _id: 155, name: 'Tasty Lemon },
    { _id: 156, name: 'Vanilla Dream }
insertedCount: 3,
insertedIds: [
    154,
    155,
    156 ]
}

Node.js MongoDB Find

In MongoDB we use the find and findOne methods to find data in a collection.

Just like the SELECT statement is used to find data in a table in a MySQL database.

Find One

To select data from a collection in MongoDB, we can use the findOne() method.

The findOne() method returns the first occurrence in the selection.

The first parameter of the findOne() method is a query object. In this example we use an empty query object, which selects all documents in a collection (but returns only the first document).

Example

Find the first document in the customers collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").findOne({}, function(err, result) {
    if (err) throw err;
    console.log(result.name);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_findone.js" and run the file:

Run "demo_mongodb_findone.js"

C:\Users\Your Name>node demo_mongodb_findone.js

Which will give you this result:

Company Inc.

Find All

To select data from a table in MongoDB, we can also use the find() method.

The find() method returns all occurrences in the selection.

The first parameter of the find() method is a query object. In this example we use an empty query object, which selects all documents in the collection.

No parameters in the find() method gives you the same result as SELECT * in MySQL.

Example

Find all documents in the customers collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_find.js" and run the file:

Run "demo_mongodb_find.js"

C:\Users\Your Name>node demo_mongodb_find.js

Which will give you this result:

[
{ _id: 58fdbf5c0ef8a50b4cdd9a84 , name: 'John', address: 'Highway 71'},
{ _id: 58fdbf5c0ef8a50b4cdd9a85 , name: 'Peter', address: 'Lowstreet 4'},
{ _id: 58fdbf5c0ef8a50b4cdd9a86 , name: 'Amy', address: 'Apple st 652'},
{ _id: 58fdbf5c0ef8a50b4cdd9a87 , name: 'Hannah', address: 'Mountain 21'},
{ _id: 58fdbf5c0ef8a50b4cdd9a88 , name: 'Michael', address: 'Valley 345'},
{ _id: 58fdbf5c0ef8a50b4cdd9a89 , name: 'Sandy', address: 'Ocean blvd 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8a , name: 'Betty', address: 'Green Grass 1'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8b , name: 'Richard', address: 'Sky st 331'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8c , name: 'Susan', address: 'One way 98'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8d , name: 'Vicky', address: 'Yellow Garden 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8e , name: 'Ben', address: 'Park Lane 38'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8f , name: 'William', address: 'Central st 954'},
{ _id: 58fdbf5c0ef8a50b4cdd9a90 , name: 'Chuck', address: 'Main Road 989'},
{ _id: 58fdbf5c0ef8a50b4cdd9a91 , name: 'Viola', address: 'Sideway 1633'}
]

Find Some

The second parameter of the find() method is an object describing which fields to include in the result.

This parameter is optional, and if omitted, all fields will be included in the result.

Example

Return the fields "name" and "address" of all documents in the customers collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}, { _id: 0, name: 1, address: 1 }).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_find_fields.js" and run the file:

Run "demo_mongodb_find_fields.js"

C:\Users\Your Name>node demo_mongodb_find_fields.js

Which will give you this result:

[
{ name: 'John', address: 'Highway 71'},
{ name: 'Peter', address: 'Lowstreet 4'},
{ name: 'Amy', address: 'Apple st 652'},
{ name: 'Hannah', address: 'Mountain 21'},
{ name: 'Michael', address: 'Valley 345'},
{ name: 'Sandy', address: 'Ocean blvd 2'},
{ name: 'Betty', address: 'Green Grass 1'},
{ name: 'Richard', address: 'Sky st 331'},
{ name: 'Susan', address: 'One way 98'},
{ name: 'Vicky', address: 'Yellow Garden 2'},
{ name: 'Ben', address: 'Park Lane 38'},
{ name: 'William', address: 'Central st 954'},
{ name: 'Chuck', address: 'Main Road 989'},
{ name: 'Viola', address: 'Sideway 1633'}
]

You are not allowed to specify both 0 and 1 values in the same object (except if one of the fields is the _id field). If you specify a field with the value 0, all other fields get the value 1, and vice versa:

Example

This example will exclude "address" from the result:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}, { address: 0 }).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

To exclude the _id field, you must set its value to 0:

Example

This example will return only the "name" field:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}, { _id: 0, name: 1 }).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Example

This example will give you the same result as the first example; return all fields except the _id field:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}, { _id: 0 }).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Example

You get an error if you specify both 0 and 1 values in the same object (except if one of the fields is the _id field):

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find({}, { name: 1, address: 0 }).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

The Result Object

As you can see from the result of the example above, the result can be converted into an array containing each document as an object.

To return e.g. the address of the third document, just refer to the third array object's address property:

Example

Return the address of the third document:

console.log(result[2].address);

Which will produce this result:

Apple st 652

Node.js MongoDB Query

Filter the Result

When finding documents in a collection, you can filter the result by using a query object.

The first argument of the find() method is a query object, and is used to limit the search.

Example

Find documents with the address "Park Lane 38":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var query = { address: "Park Lane 38" };
dbo.collection("customers").find(query).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_query.js" and run the file:

Run "demo_mongodb_query.js"

C:\Users\Your Name>node demo_mongodb_query.js

Which will give you this result:

[
{ _id: 58fdbf5c0ef8a50b4cdd9a8e , name: 'Ben', address: 'Park Lane 38' }
]

Filter With Regular Expressions

You can write regular expressions to find exactly what you are searching for.

Regular expressions can only be used to query strings.

To find only the documents where the "address" field starts with the letter "S", use the regular expression /^S/:

Example

Find documents where the address starts with the letter "S":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var query = { address: /^S/ };
dbo.collection("customers").find(query).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_query_s.js" and run the file:

Run "demo_mongodb_query_s.js"

C:\Users\Your Name>node demo_mongodb_query_s.js

Which will give you this result:

[
{ _id: 58fdbf5c0ef8a50b4cdd9a8b , name: 'Richard', address: 'Sky st 331' },
{ _id: 58fdbf5c0ef8a50b4cdd9a91 , name: 'Viola', address: 'Sideway 1633' }
]

Node.js MongoDB Sort

Sort the Result

Use the sort() method to sort the result in ascending or descending order.

The sort() method takes one parameter, an object defining the sorting order.

Example

Sort the result alphabetically by name:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var mysort = { name: 1 };
dbo.collection("customers").find().sort(mysort).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_sort.js" and run the file:

Run "demo_sort.js"

C:\Users\Your Name>node demo_sort.js

Which will give you this result:

[
{ _id: 58fdbf5c0ef8a50b4cdd9a86, name: 'Amy', address: 'Apple st 652'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8e, name: 'Ben', address: 'Park Lane 38'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8a, name: 'Betty', address: 'Green Grass 1'},
{ _id: 58fdbf5c0ef8a50b4cdd9a90, name: 'Chuck', address: 'Main Road 989'},
{ _id: 58fdbf5c0ef8a50b4cdd9a87, name: 'Hannah', address: 'Mountain 21'},
{ _id: 58fdbf5c0ef8a50b4cdd9a84, name: 'John', address: 'Highway 71'},
{ _id: 58fdbf5c0ef8a50b4cdd9a88, name: 'Michael', address: 'Valley 345'},
{ _id: 58fdbf5c0ef8a50b4cdd9a85, name: 'Peter', address: 'Lowstreet 4'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8b, name: 'Richard', address: 'Sky st 331'},
{ _id: 58fdbf5c0ef8a50b4cdd9a89, name: 'Sandy', address: 'Ocean blvd 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8c, name: 'Susan', address: 'One way 98'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8d, name: 'Vicky', address: 'Yellow Garden 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a91, name: 'Viola', address: 'Sideway 1633'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8f, name: 'William', address: 'Central st 954'}
]

Sort Descending

Use the value -1 in the sort object to sort descending.

{ name: 1 } // ascending
{ name: -1 } // descending

Example

Sort the result reverse alphabetically by name:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var mysort = { name: -1 };
dbo.collection("customers").find().sort(mysort).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_sort_desc.js" and run the file:

Run "demo_sort_desc.js"

C:\Users\Your Name>node demo_sort_desc.js

Which will give you this result:

[
{ _id: 58fdbf5c0ef8a50b4cdd9a8f, name: 'William', address: 'Central st 954'},
{ _id: 58fdbf5c0ef8a50b4cdd9a91, name: 'Viola', address: 'Sideway 1633'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8d, name: 'Vicky', address: 'Yellow Garden 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8c, name: 'Susan', address: 'One way 98'},
{ _id: 58fdbf5c0ef8a50b4cdd9a89, name: 'Sandy', address: 'Ocean blvd 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8b, name: 'Richard', address: 'Sky st 331'},
{ _id: 58fdbf5c0ef8a50b4cdd9a85, name: 'Peter', address: 'Lowstreet 4'},
{ _id: 58fdbf5c0ef8a50b4cdd9a88, name: 'Michael', address: 'Valley 345'},
{ _id: 58fdbf5c0ef8a50b4cdd9a84, name: 'John', address: 'Highway 71'},
{ _id: 58fdbf5c0ef8a50b4cdd9a87, name: 'Hannah', address: 'Mountain 21'},
{ _id: 58fdbf5c0ef8a50b4cdd9a90, name: 'Chuck', address: 'Main Road 989'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8a, name: 'Betty', address: 'Green Grass 1'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8e, name: 'Ben', address: 'Park Lane 38'},
{ _id: 58fdbf5c0ef8a50b4cdd9a86, name: 'Amy', address: 'Apple st 652'}
]

Node.js MongoDB Delete

Delete Document

To delete a record, or document as it is called in MongoDB, we use the deleteOne() method.

The first parameter of the deleteOne() method is a query object defining which document to delete.

Note: If the query finds more than one document, only the first occurrence is deleted.

Example

Delete the document with the address "Mountain 21":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myquery = { address: 'Mountain 21' };
dbo.collection("customers").deleteOne(myquery, function(err, obj) {
    if (err) throw err;
    console.log("1 document deleted");
    db.close();
});
});

Save the code above in a file called "demo_delete.js" and run the file:

Run "demo_delete.js"

C:\Users\Your Name>node demo_delete.js

Which will give you this result:

1 record deleted

Delete Many

To delete more than one document, use the deleteMany() method.

The first parameter of the deleteMany() method is a query object defining which documents to delete.

Example

Delete all documents were the address starts with the letter "O":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myquery = { address: /^O/ };
dbo.collection("customers").deleteMany(myquery, function(err, obj) {
    if (err) throw err;
    console.log(obj.result.n + " document(s) deleted");
    db.close();
});
});

Save the code above in a file called "demo_delete_many.js" and run the file:

Run "demo_delete_many.js"

C:\Users\Your Name>node demo_delete_many.js

Which will give you this result:

2 document(s) deleted

The Result Object

The deleteMany() method returns an object which contains information about how the execution affected the database.

Most of the information is not important to understand, but one object inside the object is called "result" which tells us if the execution went OK, and how many documents were affected.

The result object looks like this:

{ n: 2, ok: 1 }

You can use this object to return the number of deleted documents:

Example

Return the number of deleted documents:

console.log(obj.result.n);

Which will produce this result:

2

Node.js MongoDB Drop

Drop Collection

You can delete a table, or collection as it is called in MongoDB, by using the drop() method.

The drop() method takes a callback function containing the error object and the result parameter which returns true if the collection was dropped successfully, otherwise it returns false.

Example

Delete the "customers" table:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").drop(function(err, delOK) {
    if (err) throw err;
    if (delOK) console.log("Collection deleted");
    db.close();
});
});

Save the code above in a file called "demo_drop.js" and run the file:

Run "demo_drop.js"

C:\Users\Your Name>node demo_drop.js

Which will give you this result:

Collection deleted

db.dropCollection

You can also use the dropCollection() method to delete a table (collection).

The dropCollection() method takes two parameters: the name of the collection and a callback function.

Example

Delete the "customers" collection, using dropCollection():

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.dropCollection("customers", function(err, delOK) {
    if (err) throw err;
    if (delOK) console.log("Collection deleted");
    db.close();
});
});

Save the code above in a file called "demo_dropcollection.js" and run the file:

Run "demo_dropcollection.js"

C:\Users\Your Name>node demo_dropcollection.js

Which will give you this result:

Collection deleted

Node.js MongoDB Update

Update Document

You can update a record, or document as it is called in MongoDB, by using the updateOne() method.

The first parameter of the updateOne() method is a query object defining which document to update.

Note: If the query finds more than one record, only the first occurrence is updated.

The second parameter is an object defining the new values of the document.

Example

Update the document with the address "Valley 345" to name="Mickey" and address="Canyon 123":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myquery = { address: "Valley 345" };
var newvalues = { $set: {name: "Mickey", address: "Canyon 123" } };
dbo.collection("customers").updateOne(myquery, newvalues, function(err, res) {
    if (err) throw err;
    console.log("1 document updated");
    db.close();
});
});

Save the code above in a file called "demo_update_one.js" and run the file:

Run "demo_update_one.js"

C:\Users\Your Name>node demo_update_one.js

Which will give you this result:

1 document updated

Update Only Specific Fields

When using the $set operator, only the specified fields are updated:

Example

Update the address from "Valley 345" to "Canyon 123":

...
var myquery = { address: "Valley 345" };
var newvalues = { $set: { address: "Canyon 123" } };
dbo.collection("customers").updateOne(myquery, newvalues, function(err, res) {
...

Update Many Documents

To update all documents that meets the criteria of the query, use the updateMany() method.

Example

Update all documents where the name starts with the letter "S":

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
var myquery = { address: /^S/ };
var newvalues = {$set: {name: "Minnie"} };
dbo.collection("customers").updateMany(myquery, newvalues, function(err, res) {
    if (err) throw err;
    console.log(res.result.nModified + " document(s) updated");
    db.close();
});
});

Save the code above in a file called "demo_update_many.js" and run the file:

Run "demo_update_many.js"

C:\Users\Your Name>node demo_update_many.js

Which will give you this result:

2 document(s) updated

The Result Object

The updateOne() and the updateMany() methods return an object which contains information about how the execution affected the database.

Most of the information is not important to understand, but one object inside the object is called "result" which tells us if the execution went OK, and how many documents were affected.

The result object looks like this:

{ n: 1, nModified: 2, ok: 1 }

You can use this object to return the number of updated documents:

Example

Return the number of updated documents:

console.log(res.result.nModified);

Which will produce this result:

2

Node.js MongoDB Limit

Limit the Result

To limit the result in MongoDB, we use the limit() method.

The limit() method takes one parameter, a number defining how many documents to return.

Consider you have a "customers" collection:

customers

[
{ _id: 58fdbf5c0ef8a50b4cdd9a84 , name: 'John', address: 'Highway 71'},
{ _id: 58fdbf5c0ef8a50b4cdd9a85 , name: 'Peter', address: 'Lowstreet 4'},
{ _id: 58fdbf5c0ef8a50b4cdd9a86 , name: 'Amy', address: 'Apple st 652'},
{ _id: 58fdbf5c0ef8a50b4cdd9a87 , name: 'Hannah', address: 'Mountain 21'},
{ _id: 58fdbf5c0ef8a50b4cdd9a88 , name: 'Michael', address: 'Valley 345'},
{ _id: 58fdbf5c0ef8a50b4cdd9a89 , name: 'Sandy', address: 'Ocean blvd 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8a , name: 'Betty', address: 'Green Grass 1'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8b , name: 'Richard', address: 'Sky st 331'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8c , name: 'Susan', address: 'One way 98'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8d , name: 'Vicky', address: 'Yellow Garden 2'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8e , name: 'Ben', address: 'Park Lane 38'},
{ _id: 58fdbf5c0ef8a50b4cdd9a8f , name: 'William', address: 'Central st 954'},
{ _id: 58fdbf5c0ef8a50b4cdd9a90 , name: 'Chuck', address: 'Main Road 989'},
{ _id: 58fdbf5c0ef8a50b4cdd9a91 , name: 'Viola', address: 'Sideway 1633'}
]

Example

Limit the result to only return 5 documents:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection("customers").find().limit(5).toArray(function(err, result) {
    if (err) throw err;
    console.log(result);
    db.close();
});
});

Save the code above in a file called "demo_mongodb_limit.js" and run the file:

Run "demo_mongodb_limit.js"

C:\Users\Your Name>node demo_mongodb_limit.js

Which will give you this result:

customers

[
{ _id: 58fdbf5c0ef8a50b4cdd9a84 , name: 'John', address: 'Highway 71'},
{ _id: 58fdbf5c0ef8a50b4cdd9a85 , name: 'Peter', address: 'Lowstreet 4'},
{ _id: 58fdbf5c0ef8a50b4cdd9a86 , name: 'Amy', address: 'Apple st 652'},
{ _id: 58fdbf5c0ef8a50b4cdd9a87 , name: 'Hannah', address: 'Mountain 21'},
{ _id: 58fdbf5c0ef8a50b4cdd9a88 , name: 'Michael', address: 'Valley 345'}
]

As you can see from the result above, only the 5 first documents were returned.

Node.js MongoDB Join

Join Collections

MongoDB is not a relational database, but you can perform a left outer join by using the $lookup stage.

The $lookup stage lets you specify which collection you want to join with the current collection, and which fields that should match.

Consider you have a "orders" collection and a "products" collection:

orders

[
{ _id: 1, product_id: 154, status: 1 }
]

products

[
{ _id: 154, name: 'Chocolate Heaven' },
{ _id: 155, name: 'Tasty Lemons' },
{ _id: 156, name: 'Vanilla Dreams' }
]

Example

Join the matching "products" document(s) to the "orders" collection:

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/";

MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbo = db.db("mydb");
dbo.collection('orders').aggregate([
    { $lookup:
       {
         from: 'products',
         localField: 'product_id',
         foreignField: '_id',
         as: 'orderdetails'
       }
     }
    ]).toArray(function(err, res) {
    if (err) throw err;
    console.log(JSON.stringify(res));
    db.close();
});
});

Save the code above in a file called "demo_mongodb_join.js" and run the file:

Run "demo_mongodb_join.js"

C:\Users\Your Name>node demo_mongodb_join.js

Which will give you this result:

[
{ "_id": 1, "product_id": 154, "status": 1, "orderdetails": [
{ "_id": 154, "name": "Chocolate Heaven" } ]
}
]

As you can see from the result above, the matching document from the products collection is included in the orders collection as an array.