ExpressJs Routing Fundamentals

ExpressJS is a framework for building web applications using Node.js. One of the key features of ExpressJS is its ability to handle routing. Routing is the process of determining which function to call for a given URL. ExpressJS provides a simple and flexible way to handle routing.

Syntax

ExpressJS provides a set of methods for defining routes. The basic syntax for defining a route is as follows:

app.METHOD(PATH, HANDLER)

• METHOD is the HTTP method (get, post, put, delete, etc.)
• PATH is the URL path
• HANDLER is the function to be called when the route is requested

Example

Let's create a simple ExpressJS application with two routes.

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

app.get('/', (req, res) => {
    res.send('Hello World!')
})

app.get('/about', (req, res) => {
    res.send('About Page')
})

app.listen(3000, () => {
    console.log('Server started at http://localhost:3000/')
})

In the above code, we have defined two routes. The first route responds to requests to the root URL and the second route responds to requests to the /about URL. Both routes use the get method.

Output

Let's run our application and see the output.

Server started at http://localhost:3000/

Now if we navigate to http://localhost:3000/ in a web browser, we should see the message "Hello World!". If we navigate to http://localhost:3000/about, we should see the message "About Page".

Explanation

ExpressJS provides a number of methods for defining routes, including get, post, put, delete, all, and more. The get method is used to define a route to respond to GET requests. The post, put, and delete methods are used to define routes to respond to POST, PUT, and DELETE requests, respectively. The all method is used to define a route to respond to all HTTP methods.

The PATH parameter can be a string, a regular expression, or an array of strings and regular expressions. When a request matches a route, the HANDLER function is called with two arguments: req (the request object) and res (the response object).

Use

Routing is a fundamental part of building web applications. ExpressJS provides a simple and flexible way to handle routing. You can define routes for different HTTP methods and you can use regular expressions to match complex URL patterns. You can also use middleware functions to process requests before they reach the route handler.

Important Points

• Routing is the process of determining which function to call for a given URL.
• ExpressJS provides a simple and flexible way to handle routing.
• The basic syntax for defining a route is app.METHOD(PATH, HANDLER).
• The PATH parameter can be a string, a regular expression, or an array of strings and regular expressions.
• The HANDLER function is called with two arguments: req and res.
• You can use middleware functions to process requests before they reach the route handler.

Summary

In this article, we have learned about ExpressJS routing fundamentals. We have looked at the syntax for defining routes, and we have seen an example of a simple ExpressJS application with two routes. We have also discussed some important points to keep in mind when working with ExpressJS routing.