Express.js and MongoDB: A Comprehensive Guide
A reference for building a REST API with Express.js and the official MongoDB Node.js driver: connecting with MongoClient, then one route per operation — find all, find by id, filter, paginate with skip and limit, insert, upsert with PUT, update with PATCH, delete and count — each paired with the fetch call that uses it from a React client.
Basic Setup
Embedded on index.js to Connect:
const express = require("express");
const cors = require("cors");
const { MongoClient, ServerApiVersion, ObjectId } = require("mongodb");
const jwt = require("jsonwebtoken"); // import jwt if use JsonWeb token
require("dotenv").config(); // import env file if use environment variables after install || npm install dotenv --save|| ane Create a .env file in the root of your project:
const port = process.env.PORT || 5000;
const app = express();
// used Middleware
app.use(cors());
app.use(express.json());
// Connact With MongoDb Database
const uri = `mongodb+srv://${process.env.DB_USER}:${process.env.DB_PASS}@cluster0.krxly.mongodb.net/?retryWrites=true&w=majority`;
const client = new MongoClient(uri, {
useNewUrlParser: true,
useUnifiedTopology: true,
serverApi: ServerApiVersion.v1,
});
// Create a async fucntion to all others activity
async function run() {
try {
await client.connect();
// Create Database to store Data
const testCollection = client.db("testDatabaseName").collection("testData");
} finally {
// await client.close();
}
}
// Call the function you declare abobe
run().catch(console.dir);
// Root Api to check activity
app.get("/", (req, res) => {
res.send("Hello From NR Computers!");
});
app.listen(port, () => {
console.log(`NR Computers listening on port ${port}`);
});Get Method
Get/Access all data from MongoDB database
Server Site Code:
app.get("/service", async (req, res) => {
const result = await testCollection.find().toArray();
res.send(result);
});Client Site Code:
useEffect(() => {
fetch("http://localhost:5000/service")
.then((res) => res.json())
.then((data) => console.log(data));
}, []);Get/Access Specific data from MongoDB database with id/email
Server Site Code:
app.get("/service/:id", async (req, res) => {
const id = req.params.id;
const result = await testCollection.find({ _id: new ObjectId(id) }).toArray();
res.send(result);
});Client Site Code:
useEffect(() => {
fetch(`http://localhost:5000/service/${id}`)
.then((res) => res.json())
.then((data) => console.log(data));
}, []);Get/Access Specific data from MongoDB database with multiple queries
Server Site Code:
app.get("/service", async (req, res) => {
const query = req.body;
const result = await testCollection.find(query).toArray();
res.send(result);
});Client Site Code:
const query = {
email: "exampale@example.com",
name: "set name",
time: "set time",
};
useEffect(() => {
fetch("http://localhost:5000/service", {
method: "GET",
body: JSON.stringify(query), // send any of query by which you find data
})
.then((res) => res.json())
.then((data) => console.log(data));
}, []);Get/Access Limited data from the MongoDB database after finding the query
Server Site Code:
app.get("/service", async (req, res) => {
const query = {};
const findData = testCollection.find(query);
const result = await findData.skip(5).limit(3).toArray(); // you can also set skip & limit range dynamicly.
res.send(result);
});Client Site Code:
useEffect(() => {
fetch("http://localhost:5000/service")
.then((res) => res.json())
.then((data) => console.log(data));
}, []);Post Method
Post data without checking on MongoDB database
Server Site Code:
app.post("/service", async (req, res) => {
const service = req.body;
const result = await testCollection.insertOne(service);
res.send(result);
});Client Site Code:
const newData = {
// store new Data in Object here
name: "",
price: "",
};
fetch("http://localhost:5000/service", {
method: "POST",
headers: {
"content-type": "application/json",
},
body: JSON.stringify(newData),
})
.then((res) => res.json())
.then((result) => {
const allData = [...previusData, newData];
console.log(newReview);
});Post data With check-in MongoDB database. Better to use Put Method for this task
Server Site Code:
app.post("/service/:email", async (req, res) => {
const service = req.body.service;
const query = req.body.newQuery;
query.email = email;
const exist = testCollection.findOne(query);
if (exist) {
res.send({ result: "success" });
} else {
const result = await testCollection.insertOne(service);
res.send(result);
}
});Client Site Code:
const service = {
name: "",
price: "",
};
const newQuery = {
name: "",
time: "",
};
fetch("http://localhost:5000/service", {
method: "POST",
headers: {
"content-type": "application/json",
},
body: JSON.stringify({ service, newQuery }),
})
.then((res) => res.json())
.then((result) => {
const allData = [...previusData, newData];
console.log(newReview);
});Put Method
Update & insert Data on the database by id/email/otherQuery
Server Site Code:
app.put("/service/:id", async (req, res) => {
const id = req.params.id;
const service = req.body;
const result = await testCollection.updateOne(
{ _id: new ObjectId(id) }, // Find Data by query many time query type is "_id: id" Cheack on database
{
$set: service, // Set updated Data
},
{ upsert: true } // define work
);
res.send({ result });
});Client Site Code:
const updatedData = {
name: "",
role: "",
};
fetch(`http://localhost:5000/service/${id}`, {
method: "PUT",
headers: {
"content-type": "application/json",
},
body: JSON.stringify(updatedData),
})
.then((res) => res.json())
.then((data) => {
alert("item Updated successfully!!!");
});Patch Method
Update Data by id/email/othersQuery
Server Site Code:
app.patch("/service/:id", async (req, res) => {
const id = req.params.id;
const service = req.body;
const result = await testCollection.updateOne(
{ _id: id }, // sometime _id: new ObjectId(id)
{
$set: service,
}
);
res.send(result);
});Client Site Code:
const updatedData = {
name: "",
role: "",
};
fetch(`http://localhost:5000/service/${id}`, {
method: "patch",
headers: {
"content-type": "application/json",
},
body: JSON.stringify(updatedData),
})
.then((res) => res.json())
.then((data) => {
alert("item Updated successfully!!!");
});Delete Method
Delete Data from MongoDB Database by id
Server Site Code:
app.delete("/service/:id", async (req, res) => {
const id = req.params.id;
const result = await testCollection.deleteOne({ _id: new ObjectId(id) });
res.send(result);
});Client Site Code:
fetch(`http://localhost:5000/service/${_id}`, {
method: "DELETE",
})
.then((res) => res.json())
.then((data) => {});Count the number of arrays
Server Site Code:
app.get("/billsCount", async (req, res) => {
const count = await billCollection.countDocuments();
res.send({ count });
});Common Questions
- How do I connect Express.js to MongoDB?
- Install
express,mongodb,corsanddotenv, create aMongoClientwith the connection string from your.env, and callawait client.connect(). Then take a collection withclient.db('name').collection('items')and use it inside your route handlers. - How do I find a MongoDB document by id in Node.js?
- Wrap the id in
ObjectId:collection.findOne({ _id: new ObjectId(req.params.id) }). MongoDB stores_idas an ObjectId, not a string, so a query with the raw string from the URL matches nothing. - What is the difference between PUT and PATCH in a REST API?
- PUT replaces the whole resource — with
upsert: trueit also creates the document when it does not exist yet. PATCH changes only the fields sent, through$set, and leaves everything else as it was. - How do I paginate MongoDB results in Express?
- Read the page and size from the query string and call
collection.find().skip(page * size).limit(size).toArray(). ReturncountDocuments()alongside, so the frontend knows how many pages there are.