If you are unfamiliar with MongoDB check our guide on its basics and on how to install and use it :)
We’ll be using the official mongodb npm package. If you already have a Node.js project you are working on, install it using
npm install mongodb
If you start from scratch, create a new folder with your terminal and run npm init to start up a new Node.js project, and then run the npm install mongodb command.
Connecting to MongoDB
You require the mongodb package and you get the MongoClient object from it.
const mongo = require('mongodb').MongoClient
Create a URL to the MongoDB server. If you use MongoDB locally, the URL will be something like mongodb://localhost:27017, as 27017 is the default port.
const url = 'mongodb://localhost:27017'
Then use the mongo.connect() method to get the reference to the MongoDB instance client:
mongo.connect(url, {
useNewUrlParser: true,
useUnifiedTopology: true
}, (err, client) => {
if (err) {
console.error(err)
return
}
//...
})
Now you can select a database using the client.db() method:
const db = client.db('kennel')
Create and get a collection
You can get a collection by using the db.collection() method. If the collection does not exist yet, it’s created.
const collection = db.collection('dogs')
Insert data into a collection a Document
Add to app.js the following function which uses the insertOne() method to add an object dogs collection.
collection.insertOne({name: 'Roger'}, (err, result) => {
})
You can add multiple items using insertMany(), passing an array as the first parameter:
collection.insertMany([{name: 'Togo'}, {name: 'Syd'}], (err, result) => {
})
Find all documents
Use the find() method on the collection to get all the documents added to the collection:
collection.find().toArray((err, items) => {
console.log(items)
})
Find a specific document
Pass an object to the find() method to filter the collection based on what you need to retrieve:
collection.find({name: 'Togo'}).toArray((err, items) => {
console.log(items)
})
If you know you are going to get one element, you can skip the toArray() conversion of the cursor by calling findOne():
collection.findOne({name: 'Togo'}, (err, item) => {
console.log(item)
})
Update an existing document
Use the updateOne() method to update a document:
collection.updateOne({name: 'Togo'}, {'$set': {'name': 'Togo2'}}, (err, item) => {
console.log(item)
})
Delete a document
Use the deleteOne() method to delete a document:
collection.deleteOne({name: 'Togo'}, (err, item) => {
console.log(item)
})
Closing the connection
Once you are done with the operations you can call the close() method on the client object:
client.close()
Use promises or async/await
I posted all those examples using the callback syntax. This API supports promises (and async/await) as well.
For example this
collection.findOne({name: 'Togo'}, (err, item) => {
console.log(item)
})
Can be used with promises:
collection.findOne({name: 'Togo'})
.then(item => {
console.log(item)
})
.catch(err => {
console.error(err)
})
or async/await:
const find = async () => {
try {
const item = await collection.findOne({name: 'Togo'})
} catch(err => {
console.error(err)
})
}
find()
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