Create Backend

REST API using Express.js

For detailed description:

https://expressjs.com/en/starter/installing.html

1. Create packge.json

   npm init
   

   • Reference

2. Create Entry Point file server.js

3. Create HTTP Server in server.js → Use express

   npm install express
   

4. Create requests.http and write the server requests there and click on send request

   get <http://localhost:4000/users>
   

5. Add API Routing

   Syntax: app.METHOD ( path , request handler )

   • app: This is an instance of an Express application
   • METHOD: This represents an HTTP method → get, post, put, delete
   • path: This is the endpoint of the API
   • requestHandler: This is a function that gets executed when the route is matched. It typically takes two arguments, req (the request object) and res (the response object) (req, res) => {}

   app.get('/users', (req, res) => {
       res.send({message: 'All Users'});
   });
   

6. Parametrized Request

   1. This route handles GET requests to /users/:id, where :id is a dynamic parameter representing the user ID.
   2. If the user is found, it sends a JSON response with the user data; if not, it sends a 'User not found' message.
   3. Making Request → get http://localhost:4000/users/1

   // Send 1 user by id
   app.get('/users/:id', (req, res) => {
       const userId = Number(req.params.id);
       //  Search user by id in usersList array 
       let userById = usersList.find(user=>user.id==userId);
       if(userById === undefined){
           res.send({message: 'User not found'});
       }
       else{
           res.send({message: 'User by Id', payload: userById});
       }
   });
   

Making HTTP requests

For initial learning stages , we use a pseudo Client side application called REST Client.

Postman can also be used for testing the REST API.

REST Client

Installation

VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=humao.rest-client

Usage:

1. Create a file names requests.http in folder of server.