Express Tutorial: HTTP Requests in Express.js

Requests and Routing

HTTP requests are binary information packets that a computer or client sends to another computer or server to communicate.

Routing is basically defined as the process of selecting a path for traffic or request in a network or in a web framework. In Express, we can access web pages, files, images, scripts, stylesheets, etc. at different paths set by route. To define a route in Express, we use app.method (path, handler).

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App.method (Path, Handler)

This is a function that is used to define various routes for different types of requests. Path is address of route and handler is the function that will receive the request and give a response to that request.

HTTP Requests Methods in Express JS

Types of Request Methods for Routes (app.method(path, handler))

GET and POST Requests in Express JS

Let’s take an example of a /home route. In this example, we have defined a route at  http://localhost:3000/home. The server receives a get type request when we access this address. After receiving the request, a callback function defined in app.method gets executed, which sends the string  “Welcome to Homepage” as a response to the client

After accessing  http://localhost:3000/home, you will see the following response on the browser.

//imports express module
let express = require('express');
//initializes express app
let app = express();

//creates get function with request and response parameters
app.get('/home', function(req, res){

    //sends response to client or browser
    res.send("Welcome to Homepage");

});
//listens to server at port 3000
app.listen(3000);

Now, just try to access different routes without defining. For example, we haven’t defined any route in the above code for path  /login. You will see Cannot GET / Login response on requesting this address.

Now to check the POST request method, we will need to use cURL or any app for sending a POST request. I will use Insomnia REST Client for sending and receiving requests and responses respectively. It allows you to select an HTTP request type, set path on which the request has to be sent, and shows a response.

GET and POST Requests in Express JS

Let’s take another example by defining GET and POST request at the same route.

//imports express module
let express = require('express');
//initializes express app
let app = express();

//creates get function with request and response parameters
app.get('/home', function(req, res){

    //sends response to client or browser
    res.send("Welcome to GET");

});
//creates post function with request and response parameters
app.post('/home', function(req, res){

    //sends response to client or browser
    res.send("Welcome to POST");

});

//listens to server at port 3000
app.listen(3000);

GET Request Output in Express JS

When you will access /home route with GET request, you will see Welcome to GET response.

POST Request Output in Express JS

But, when you access /home route with a POST request, you will see Welcome to POST response.

PUT and DELETE Requests in Express JS

Similarly, modify the code to check PUT and DELETE request.

//imports express module
let express = require('express');
//initializes express app
let app = express();

//creates get function with request and response parameters
app.delete('/home', function(req, res){

    //sends response to client or browser
    res.send("Welcome to DELETE");

});
//creates post function with request and response parameters
app.put('/home', function(req, res){

    //sends response to client or browser
res.send("Welcome to PUT");

});

//listens to server at port 3000
app.listen(3000);

You will see Welcome to PUT response for your PUT method route and Welcome to DELETE response for your DELETE method route.

Outputs for PUT and DELETE Requests

All Requests Route in Express.js

In some scenarios, we have to use all the methods for a single route. For example, in middleware, we use this. Look at the code below, it has a route with all method. It will respond to all HTTP requests. The response will be the same for all HTTP requests no matter if it is GET, POST, DELETE or PUT.

//imports express module
let express = require('express');
//initializes express app
let app = express();

//creates all function with request and response parameters
app.all('/home', function(req, res){

    //sends response to client or browser
    res.send("Welcome to Home");

});

//listens to server at port 3000
app.listen(3000);

In the next tutorial, you will learn how to add static and dynamic routing in Express JS.

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