<h2>Introduction to the course</h2>Express.js is a popular JavaScript framework for building web applications. It is built on top of the Node.js platform and provides a simple, flexible, and minimalistic interface for creating web servers and building web applications.<h2>Who is this course for?</h2>Express.js is primarily for developers who are building web applications using JavaScript and the Node.js platform. It is particularly well-suited for building web servers, REST APIs, and real-time applications.

Express.js

<h2>What does this section cover?</h2>In Express.js, the Router class allows you to create modular, mountable route handlers.In this section, we will be uncovering the router class and the methods of the router class which specify the behavior of the router.

Router Class

<h2>What does this lesson cover?</h2>In this lesson, we will be defining Express.js and how it works, the basic terminology in Express.js before diving into its benefits, and the reason behind the pairing of Node and Express.js.The lesson is equipt with lesson challenges to help users better understand Express.js.

Introduction

<h2>What does this lesson cover?</h2>This lesson uncovers the web application framework of Express.js. We will be covering how Express.js handles HTTP requests with various methods. This lesson depicts each method separately with lesson quizzes and standard code examples that shape the learner&#x27;s understanding of the subject.

Request Methods

<h2>What does this lesson cover?</h2>In this lesson, we will be covering the core concepts of Express.js.They are Rest API, the Request and Response Protocol between client and server communications, and Routers,The lesson is equipt with lesson quizzes that will help guide you through the quiz.

Core Concepts

<h2>What does this lesson cover?</h2>In this lesson, we will be covering the methods of the response object and a generalization of their behavior in code.This lesson is equipt with supporting lesson quizzes and code examples that will guide you through the topic.

Methods

<h2>What does this lesson cover?</h2>We will be talking about the Response object. the response object (res) represents the HTTP response that an application sends when it receives an HTTP request. This lesson uncovers the methods of the response object, their usage, and structure in code.

Response

<h2>What does this lesson cover?</h2>Here we&#x27;ll be getting used to the Express.js environment, to do so of course, we&#x27;ll need to install it first.This lesson offers a step-by-step guide to installing the Express.js Environment.

Installation

Lesson Challenge

Request: Intro

A request or more well-known req is an object that is a part of the request-response protocol that reads in the client-side calls, makes HTTP requests, and manages data.

Here’s an example of the req object in Express.js:

We’ve created a route(a combination of a URL path and an HTTP web that indicates the behavior of an application when a client makes a request to that path) that listens for GET requests to the path <samp>/tarantino/:id </samp>and sends a response with a message that includes the value of the id parameter.

The value of the id parameter is available in the <samp>req.params </samp>object, which we will refer to in further lessons.

Fill Missing

Complete the code by outputting the result of a user’s id through the parameter<samp> /:userid</samp>.

Methods: Overview

In the web application framework of Express.js, the below-mentioned methods can be used to handle HTTP requests:

▸ GET: Used to fetch information from the server.▸ POST: Used to send data to the server for creating or renewing a resource.▸ PATCH: Used to apply partial modifications to a resource.▸ PUT: Used to send data to the server to create or update a resource. This method is typicallyused when you want to update a resource without having to retrieve it first.▸ DELETE: Used to delete a resource in the server.▸ HEAD: Used to fetch the header information.▸ OPTIONS: Used to describe the communication options for a resource.

We will be getting into examples in the following quiz.

The GET method

In this, and upcoming lessons we will be focusing on the behavior and structure of request methods in code.

The GET request method is used to fetch information from the server, handling the GET request can be accomplished with the <samp>app.get() </samp>method that takes on two arguments: the path of the requested resource, and a callback function that will be executed when the request is received.

Here&#x27;s an example of how you might use the GET method:

In the above example, when a GET request is made to the <samp>/users </samp>route, the callback function will be executed, and the string “<samp>Fetching users list</samp>” will be sent as the response to the client.

Additional parameters can be passed to the <samp>app.get() </samp>method, defining the HTTP status code, headers, etc., like so:

In the code snippet above, the response will have a status code of <samp>200 </samp>(OK) and headers.

Make a GET request to the<samp> /usr/hi.usr route</samp>.

The POST method

The POST method is utilized to create a new resource by submitting an HTTP request to the server.

Find the structure and syntax of the POST method in the code example below:

With the <samp>User.create()</samp> method, we’ve created a new user in the database, if there was an error, a response with the <samp>404 </samp>status code will be sent, if everything goes well, a response with a status code of <samp>202 </samp>will be sent.

The DELETE method

The DELETE request method is used to delete a resource in the server.

In the code example above, the DELETE method is being used to delete a user with a specific ID. The <samp>req.params.id </samp>property is used to get the user&#x27;s ID from the URL parameters, and then delete it with the <samp>findByIdAndDelete</samp> method. If an error occurs, the server responds with a status code of <samp>500</samp>, and if successful, the deleted user object.

The DELETE method should be used with caution. It permanently removes the resource from the server and cannot be undone.

Delete a <samp>barbie </samp>from the collection by getting the ID of the barbie from the URL parameters.

The HEAD method

The HEAD method in Express.js is used to send a request for the headers of a resource. It is similar to the GET method, but it does not return the resource itself. Instead, it only returns the headers of the resource, which can include information such as the content type, content length, and last modified date.

Here’s an example of the HEAD method in some code:

In this example, the response headers will include the type, length, and last modified date of the content.

We finished the code off with the <samp>res.end() </samp>method to send the headers to the client.

The OPTIONS method

During client-server communication, a client can make an OPTIONS request. The server with thus respond with the HTTP methods that the client is allowed to use when accessing the resource. This can include methods such as GET, HEAD, POST, PUT, DELETE, and PATCH.

Let’s take a look at the following example:

The &#x27;Allow&#x27; header in the response defines the methods the user is permitted to use (in our case: <samp>GET</samp>, <samp>POST</samp>, <samp>PUT</samp>, <samp>PATCH </samp>when accessing the <samp>/coworkers</samp> resource. Finally, we set the status code to <samp>200 </samp>(OK) and ended the response.

Complete the code with the OPTIONS method.

Note: The client is only permitted to use the <samp>DELETE </samp>method in the <samp>/items </samp>resource.

<h2>What does this section cover?</h2>This section introduces newbies to the absolute fundamentals and basics of Express.js. After defining Express.js and its perks, we&#x27;ll identify Express.js characteristics such as routers, request and response protocol, and REST APIs.

Get Started

<h2>What does this lesson cover?</h2>In this lesson, we will be covering one-half of the response-request protocol, the response half.This serves as an introduction and a behavioral analysis of how requests work in Express.js with code examples that outline the preservation of the topic at hand.

Request and Response

<h2>What does this section cover?</h2>In Express.js, the Router class allows you to create modular, mountable route handlers, the Router class additionally provides various methods that will be gradually uncovered.

Express.js

Achievements

The DELETE method

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