How to Create an API using Express.js

Express.js is a popular web application framework for Node.js that provides a robust set of features for building web and mobile applications. One of the key capabilities of Express.js is its ability to create APIs for interacting with client-side applications. In this article, we will explore how to create an API using Express.js.

Step 1: Install Node.js and Express.js

First, make sure you have Node.js installed on your machine. You can download and install the latest version of Node.js from the official website. Once you have Node.js installed, you can use npm (Node Package Manager) to install Express.js by running the following command in your terminal:

npm install express

Step 2: Set Up Your Express.js Project

Create a new directory for your project and navigate to it in the terminal. Then, initialize a new Node.js project by running the following command:

npm init -y

This will create a package.json file in your project directory, which will store all the information about your project and its dependencies. Next, create a new file called app.js and add the following code:


const express = require('express');
const app = express();
const port = 3000;

app.listen(port, () => {
console.log(`Server is running on port ${port}`);
});


Step 3: Define Your API Endpoints

Now that you have set up your Express.js project, you can define your API endpoints by adding route handlers to your app.js file. For example, you can create a simple GET endpoint that returns a list of users by adding the following code:


app.get('/users', (req, res) => {
const users = ['John', 'Jane', 'Doe'];
res.json(users);
});


Step 4: Test Your API

Finally, you can test your API by running your Express.js server and sending HTTP requests to your defined endpoints. To start your server, run the following command in your terminal:

node app.js

Once your server is running, you can use tools like Postman or a web browser to send GET requests to http://localhost:3000/users and see the list of users returned by your API.

And there you have it – you have successfully created an API using Express.js! Express.js provides a flexible and powerful platform for building APIs, and with the right knowledge and practice, you can create robust and efficient APIs for a wide range of applications.