Building Your First API Endpoint with Node.js and Express.js

APIs (Application Programming Interfaces) are the backbone of modern web applications, allowing communication between different services and applications. If you’re new to API development, building a simple endpoint using Node.js and Express.js is an excellent way to get started. In this guide, you’ll learn how to set up a basic API endpoint that returns JSON data, making it easy for you to grasp the fundamentals of API development. 

 

What is an Endpoint in a REST API? 

An endpoint is a specific URL where an API receives requests and sends responses. Each endpoint is associated with a particular HTTP method (such as GET, POST, PUT, DELETE) and is used to interact with the API. 

For example, if you are building a food ordering app, an API endpoint like: 

GET /restaurants
 

could return a list of available restaurants. 

In this tutorial, we’ll build a GET endpoint that returns sample data. 

 Also read: How to Set Up a Simple Node.js Server in 5 Minutes

Setting Up an Express.js Route for a GET Request 

Step 1: Install Node.js and Express 

First, ensure you have Node.js installed on your machine. If not, download it from nodejs.org. 

Then, create a project directory and initialize a Node.js project: 

mkdir my-api 
cd my-api 
npm init -y 
 

Next, install Express.js: 

npm install express 
 

Step 2: Create a Basic Express Server 

Create an index.js file and add the following code: 

const express = require('express'); 
const app = express(); 
const PORT = 3000; 
 
app.get('/', (req, res) => { 
    res.send('Welcome to my first API!'); 
}); 
 
app.listen(PORT, () => { 
    console.log(`Server is running on http://localhost:${PORT}`); 
}); 
 

Now, run the server: 

node index.js
 

Visit http://localhost:3000 in your browser, and you should see Welcome to my first API! displayed. 

 

Returning Data as a JSON Response 

Instead of sending plain text, let’s return JSON data. Modify the index.js file to create a new GET endpoint: 

app.get('/api/data', (req, res) => { 
    const sampleData = { 
        name: "John Doe", 
        age: 30, 
        occupation: "Software Developer" 
    }; 
    res.json(sampleData); 
}); 
 

Restart your server and visit http://localhost:3000/api/data. You should see: 

{ 
    "name": "John Doe", 
    "age": 30, 
    "occupation": "Software Developer" 
} 
 

 

Testing the Endpoint with Postman or a Browser 

Testing with a Browser 

For simple GET requests, you can directly visit http://localhost:3000/api/data in your browser, and the JSON response will be displayed. 

Testing with Postman 

For more advanced testing, download Postman and follow these steps: 

• Open Postman and create a new GET request. 

• Enter http://localhost:3000/api/data in the request URL. 

• Click “Send.” 

• You should see the JSON response displayed in Postman. 

 Read: How to create a REST API with Node.js and Express

Conclusion 

Congratulations! 🎉 You’ve successfully built your first API endpoint using Node.js and Express.js. You now understand: 

• What an API endpoint is. 

• How to create a basic Express server. 

• How to return JSON data in a response. 

• How to test your API using Postman or a browser. 

From here, you can expand your API by adding more endpoints, handling different HTTP methods, and connecting to a database. Happy coding!