Getting started with Express.js

  • Post category:Express
  • Reading time:2 mins read

To install express, write the command npm i express. Now, before using express I would recommend you to install postman for API testing.

How to use express?

The first step is to write npm init command in the terminal to create a new Node.js project by generating a package.json.

Let’s see a simple example of using express.

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

app.get('/', (req, res) => {
    res.status(200).json({
        display: 'welcome',
        name: 'codeyup',
    });
});

const port = 8000;
app.listen(port, () => {
    console.log(`current port: ${port}`);
});

You can now check the API response in the browser network tab or using the postman. I have attached a image below in which I used postman for checking the above GET API call response.

How to use express

Explanation:

  • Import express in app.js file and now create a variable with any name such as app and assign express() function to this variable. This function will add a bunch of methods (such as get, post, etc) to the variable app.
  • app.get is used for GET requests to the root URL (‘/’). When a GET request is made to ‘/’, the provided callback function is executed.
  • req (request) contains information about the HTTP request.
  • res (response) is used to send a response back to the client.
  • Inside the callback function, we set the HTTP status code of the response to 200 (i.e success) and send a JSON response with two properties: display with the value ‘welcome’ and name with the value ‘codeyup’.
  • In variable port, I have given the value 8000 and this port number will be used by the Express application to listen for incoming connections.
  • I used app.listen() to start the server and makes it listen for connections on the specified port (8000).
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