Basic Routing

Routing is a fundamental concept in Express.js that enables you to handle HTTP requests and map them to specific routes. Here's an overview of basic routing in Express:

Route Types

There are two types of routes in Express:

1. HTTP Methods: Represented by verbs like GET, POST, PUT, etc.
2. Paths: Represented by strings, used to identify the endpoint.

Creating Routes

To create a route, you can use the app object (which is an instance of Express) and specify the HTTP method and path:

javascript
const express = require('express');
const app = express();
// GET /hello
app.get('/hello', (req, res) => {
  res.send('Hello World!');
});
// POST /users
app.post('/users', (req, res) => {
  // Handle user creation logic here
});

In this example:

• GET /hello maps to the /hello path and responds with a "Hello World!" message when an HTTP GET request is made.
• POST /users maps to the /users path and will handle user creation logic.

Example Use Case

Let's create a simple API that allows users to perform CRUD (Create, Read, Update, Delete) operations on books:

javascript
const express = require('express');
const app = express();
// Create route for getting all books
app.get('/books', (req, res) => {
  const books = [
    { id: 1, title: 'Book 1' },
    { id: 2, title: 'Book 2' }
  ];
  res.json(books);
});
// Create route for creating a new book
app.post('/books', (req, res) => {
  const newBook = req.body;
  // Save the new book to the database
  console.log(newBook);
  res.status(201).send('Book created successfully!');
});
// Start the server
const port = 3000;
app.listen(port, () => {
  console.log(Server listening on port ${port});
});

In this example:

• GET /books returns a JSON array of all books.
• POST /books creates a new book and saves it to the database.

Route Parameters

You can also define routes with parameters using the following syntax:

javascript
app.get('/users/:id', (req, res) => {
  const userId = req.params.id;
  // Handle user retrieval logic here
});

In this example:

• GET /users/123 will pass 123 as the value of userId.

This is a basic overview of routing in Express.js. You can explore more advanced concepts like route middleware, error handling, and parameter validation to build robust APIs.