#30 Introduction to Express JS | Working with Express JS | A Complete NODE JS Course

Summary

In this introduction to Express.js, viewers learn about its role as a minimal and flexible web application framework for Node.js. The video emphasizes how Express simplifies the development process by reducing the amount of code required to build applications. It guides users through the installation of Express, creating a basic server, and handling routes for GET and POST requests. The session highlights the ease of sending responses, whether text, HTML, or JSON, showcasing the framework's efficiency in building robust web applications. Ultimately, this lesson serves as a foundational step for developers looking to leverage Express.js in their projects.

Takeaways

• 😀 Express.js is a free and open-source web application framework for Node.js that simplifies application development.
• 😀 It minimizes the amount of code developers need to write by providing built-in classes and functions.
• 😀 Express is popular in Node.js application development and is considered a standard framework.
• 😀 The framework offers robust features, including complex routing, middleware handling, and server-side rendering.
• 😀 Developers can organize their applications using the MVC (Model-View-Controller) architecture with Express.
• 😀 To start using Express, a package.json file must be generated using the command 'npm init'.
• 😀 The Express package can be installed via npm with the command 'npm install express'.
• 😀 The entry point for an Express application is usually defined in the package.json file, commonly as app.js.
• 😀 Routes in Express are defined using HTTP methods (GET, POST, etc.) combined with the URL.
• 😀 Responses can be sent in various formats, including plain text, HTML, and JSON, using appropriate methods like send() and json().

Q & A

What is Express.js?

Express.js is a free and open-source web application framework for Node.js that simplifies the development of web and mobile applications by allowing developers to write less and simpler code.

How does Express.js improve the coding experience compared to vanilla Node.js?

Express.js reduces the complexity of Node.js applications by providing built-in classes and functions, allowing developers to achieve complex functionalities with minimal lines of code.

What are some features provided by Express.js?

Express.js includes features such as complex routing, easier handling of requests and responses, middleware integration, server-side rendering, and more.

How do you create a new project in Express.js?

To create a new project in Express.js, you generate a package.json file using the command 'npm init', which sets up the project's metadata and dependencies.

What command is used to install Express.js?

You can install Express.js using the command 'npm install express'.

What is the significance of the 'app.js' file in an Express.js project?

'app.js' is designated as the entry point for the application, where all configurations and route definitions for Express.js will be kept.

How do you start an Express.js server?

To start an Express.js server, you call the 'listen' method on the Express application object, passing in the port number and a callback function to execute once the server is ready.

What is the difference between handling GET and POST requests in Express.js?

GET requests are handled using the 'get' method, while POST requests are managed using the 'post' method on the Express application object.

How do you send a JSON response in Express.js?

To send a JSON response in Express.js, you use the 'json' method on the response object, which sets the content type to 'application/json'.

Why is Express.js considered a standard in Node.js application development?

Express.js is widely used and recognized for its minimalism and flexibility, making it a standard choice among developers for building web applications with Node.js.

Outlines

00:00

😀 Introduction to Express.js

In this section, we are introduced to Express.js, a free and open-source web application framework for Node.js. It is described as a minimal and flexible framework that simplifies Node.js application development by allowing developers to write complex functionalities with minimal code. Express.js is built entirely on Node.js, making it one of the most popular frameworks for application development. Key features include robust routing, middleware handling, and server-side rendering. The section emphasizes how Express.js streamlines the development process, enabling a faster and simpler approach to writing Node.js applications, while also supporting the MVC architecture for organizing code.

05:01

😀 Setting Up Express.js

This part focuses on the practical steps to set up Express.js in a project. The process begins with creating a project folder and generating a `package.json` file using the command 'npm init'. Next, Express is installed using 'npm install express', which adds Express as a dependency and creates a 'node_modules' folder containing the framework's code and its own dependencies. The section then guides the user in creating an `app.js` file, importing the Express package, initializing the app, and starting the server on port 3000, demonstrating the foundational setup required for an Express application.

10:02

😀 Handling Routes and Responses

In this segment, the tutorial explains how to handle routes in an Express application. It illustrates the use of the `get` method to respond to GET requests at the root URL by sending a simple text response. The section also highlights the ability to send HTML and JSON responses, detailing how to format the responses accordingly. For HTML responses, the text is wrapped in an H4 element, while for JSON, the content type is set to application/json. The tutorial emphasizes the distinction between handling GET and POST requests, introducing the `post` method for managing POST requests and indicating that separate routes must be defined for different HTTP methods.

15:04

😀 Conclusion and Next Steps

The final part summarizes the key takeaways from the session, reiterating the advantages of using Express.js over vanilla Node.js. It underscores how Express reduces the amount of code developers need to write while providing essential features for web development. The section hints at future lessons where deeper exploration of Express.js will occur, including API creation, while inviting viewers to ask questions and thank them for their engagement.

Keywords

💡Express.js

Express.js is a free and open-source web application framework for Node.js, designed to simplify the development of web and mobile applications. It is a minimal and flexible framework that allows developers to build complex applications with a significantly reduced amount of code compared to using core Node.js. In the video, Express.js is highlighted as a crucial tool for writing Node.js applications faster and easier, showcasing its ability to handle complex routing and middleware effectively.

💡Node.js

Node.js is a runtime environment that allows JavaScript to be run on the server side, enabling developers to use JavaScript for both client and server-side programming. The video emphasizes that Express.js is built on top of Node.js, which means it inherits the capabilities of Node.js while providing additional functionalities that streamline the web development process. This foundation allows developers to leverage the non-blocking, event-driven architecture of Node.js for building efficient web applications.

💡Middleware

Middleware in Express.js refers to functions that have access to the request and response objects and can modify them or end the request-response cycle. The video mentions middleware as a feature of Express.js that enhances the ability to handle requests, manage errors, and facilitate additional functionalities within the application. For instance, middleware can be used for logging requests, parsing request bodies, and authenticating users.

💡Routing

Routing is the process of defining how an application responds to client requests for specific endpoints, which consist of a URL and an HTTP method (GET, POST, etc.). The video explains that Express.js simplifies routing by providing methods such as app.get() and app.post(), allowing developers to define routes for different types of requests easily. This ability to manage routing effectively is crucial for building dynamic and responsive web applications.

💡HTTP Methods

HTTP methods are standardized requests used to interact with resources on the web, including GET, POST, PUT, and DELETE. The video outlines how Express.js utilizes these methods to differentiate between various actions that can be performed on the same endpoint. For example, while a GET request retrieves data from the server, a POST request typically sends data to be processed by the server.

💡package.json

The package.json file is a configuration file for Node.js projects that contains metadata about the project, including its name, version, dependencies, and entry point. In the video, the creation of this file is demonstrated through the npm init command, which guides the developer in specifying essential project information. This file is critical for managing project dependencies and scripts, and it enables seamless integration with npm (Node Package Manager).

💡npm (Node Package Manager)

npm is the default package manager for Node.js, allowing developers to install, manage, and share packages or modules in their projects. The video showcases npm commands such as npm init for creating a package.json file and npm install for adding dependencies like Express.js. npm facilitates the use of third-party libraries and tools, greatly enhancing productivity in Node.js development.

💡app.js

app.js is the designated entry point for the Express.js application, where the main application logic and configurations are defined. The video details how the app.js file is created and populated with code to require the Express framework and set up the server. This file is central to organizing the application and is where routes and middleware are typically defined to handle incoming requests.

💡Server Listening

Server listening refers to the state in which a server is actively waiting for incoming client requests on a specified port. The video illustrates this concept when discussing the app.listen() method, which sets the server to listen on a designated port (e.g., 3000). This is a fundamental aspect of web servers, as it allows them to process requests and send responses to clients.

💡Response Object

The response object in Express.js is an instance that is used to send a response back to the client after processing a request. The video describes how to use the response object to send different types of responses, such as text and JSON, to the client. Understanding the response object is essential for effectively communicating the outcome of client requests and delivering data in various formats.

Highlights

Introduction to Express.js, a minimal and flexible web application framework for Node.js.

Express.js simplifies complex Node.js code, allowing for quicker development with fewer lines of code.

Emphasis on Express.js being built entirely on Node.js, making it a standard framework in the Node.js ecosystem.

Overview of Express's features including complex routing, middleware handling, and server-side rendering.

Express promotes organized application structure using MVC architecture.

Demonstration of generating a package.json file for a new Express project using npm.

Step-by-step guide on installing Express using npm, which updates package.json with a new dependencies field.

Creation of an app.js file as the main entry point for the Express application.

Explanation of how to import the Express package and create an Express application instance.

Introduction to creating a server with the listen method, specifying port number and callback function.

Demonstration of handling routes with Express, particularly GET requests to the root URL.

Usage of response methods such as send and json for sending responses back to the client.

Setting status codes before sending responses, showcasing the importance of HTTP status management.

Handling POST requests and defining a route for processing such requests in the Express application.

Conclusion emphasizing the efficiency of Express.js in reducing code complexity compared to vanilla Node.js.

Transcripts

hello and welcome to another section of

this complete node.js course in this

section we will learn what is express.js

and why do we use it

express.js is a free and open source web

application framework for node.js

Express is a minimal and flexible

node.js web application framework that

provides a robust set of features for

web and mobile application development

in simple words we can say that Express

helps us develop node.js application by

writing minimum node.js code it

simplifies complex node.js codes with

simple one or two line of codes

so Express is a node.js framework

this means that express.js provides some

built-in classes and functions which we

can use while developing a web

application and we can write complex

functionalities with simple one or two

line of code

without Express if we try to write the

same functionality with core node.js the

number of line of code can be large and

we as a developer will have to write

some complex Logics to achieve the same

thing but with express it can be done

with few line of codes and the

complexity of the code is taken away by

Express as the functionality is already

defined by this framework right

so remember that Express is completely

built on node shares that means behind

the scenes Express is built 100 using

node.js

it is also one of the most popular

node.js Frameworks there are few other

Frameworks as well but Express has

become kind of a standard in node.js

application development

Express contains a very robust and very

useful set of features things like

complex routing easier handling of

request and responses adding middleware

server side rendering and many more

things are all included out of the box

with Express

Express allows us to write node.js

application faster and also simpler by

providing us developers a predefined

method for almost every complex task in

node.js

and with Express we can also organize

our application to MVC architecture

which is very popular software

architecture pattern that we will also

explore a bit during this course

so again Express is a node.js framework

which help developers write node.js

program in a simple and much faster way

Express makes a developer's life with

node.js very much easier

so now that we know what is expressed

and why should we use express instead of

using vanilla node.js to write node.js

code let's now go ahead and install

express.js for our project let's go to

vs code

here I have created a brand new project

so this is our project folder with this

name node.js with Express

now the first thing which I am going to

do here is for this project I am going

to generate a package.json file and to

do that let's open Terminal let's go to

this new terminal option and it is going

to open a new terminal

here to generate a package.json file for

the project all we have to do is we have

to type this npm command npm init if I

press enter

it is going to ask a bunch of questions

so let me move this terminal a bit up so

that it will be more readable so first

of all it is asking for the package name

now here you can provide a package name

and that package name should be URL

friendly the words in that package them

should not be separated by spaces it

should be separated by a hyphen like you

can see in this example okay so I'm

going to use this same default name for

the package name for my project all

right so here I will not provide any

name so if I press enter it is going to

use this default name

and for the version also I will keep the

version as 1.0.0 let's press enter

description I don't want to give any

description or let's say

learning express.js with node.js

let's press enter

so here it is asking for the file name

which is going to be the entry point for

this project by default it is specifying

this index.js so if you don't provide

any name it is going to use this

index.js as the entry point but here I

want to call my file which is going to

be the entry point for this project as

app.js

okay so I will provide that name let's

press enter test command we don't have

any git repository we don't have any

keywords I don't want to provide any

keywords author here I will put my name

let's press enter license let's use the

default one this ISC license let's press

enter and now it is asking whether this

content for the package.json file is

okay or not so basically when I press

enter here it is going to generate the

package.json file and in that

package.json file this is going to be

the content so here vs code is

confirming whether this content is okay

for me or not for the package.json file

so basically this content is okay for me

so I will simply press enter and now you

will notice that a file with this name

package.json has been created here

and in this package.json file we have

all the configuration related data for

this project for example the name of the

project version of the project

description what is going to be the

entry point for the project who is the

author what is the license this project

is using and so on

okay let me go ahead and let me clear

the console by typing this CLS command

which

and the next thing which I want to do is

I want to install Express for this

project

and to install Express we are going to

use another npm command npm install

so using this npm install command we can

install a package from npm Repository

here the package which we want to

install is called as Express

so I will specify that name and when I

press enter it is going to install that

package so the package is being

installed

and once this package is installed you

will notice that in this package.json

file a new field called dependencies

have been added and in that field we

have this Express listed

so basically this Express is going to be

a regular dependency for this project

the code which we are going to write

that depends on this Express package

and with that a folder called node

modules has also been created and in

this folder you will see that we have a

folder called Express and in this folder

we have all the code all the files

related to express.js framework

now you will also ask what are these

folders for well this Express GS

framework it might have its own

dependencies so in order for this

express.js framework to work properly we

also need to install those dependencies

so behind the scenes when we installed

express.js the dependencies for this

express.js were also installed and these

are those dependencies

all right

now the next thing which I'm going to do

is I am going to create an app.js file

so inside this project folder I am going

to create a new file I will call it

app.js

and this file this app.js is going to be

our entry point

okay if you see in the package.json

for the entry point for this main we

have specified app.js so this app.js is

going to be our entry point and in this

app.js we are going to keep all the

configuration related to express.js

all right now let's go ahead and let's

require the Express package or let's

import Express package now keep in mind

that this Express is a third party

package so here we are going to import a

third party package now we have already

learned how to import a package for that

we use this require function

to this require function we need to pass

the package name within single quotes So

the package name here is Express

now when we are requiring this Express

package what this line of code will do

is it is going to return IF function

and we want to assign that function to a

variable so here I'm going to create a

variable and I will call it express

and to this Express I want to assign the

function which this Express package is

going to return

and once that function is assigned to

this Express variable I want to call

that function so to call that function

on this Express variable

we can use a set of parentheses so here

we are calling the function which this

line of code has returned and which is

assigned to this Express variable

and now when we are calling that

function it is going to return an object

so let's go ahead and let's store that

object in a variable and let's call that

object f

so this F variable here is going to

store an object and in that object we

have a bunch of methods which we can use

in our node.js application

for example let's say we want to create

a server

to create a server on this app object we

are going to have a method called listen

so this listen method what it is going

to do is it is going to create a server

and then it will also listen to the

requests on that server

now to this listen method we need to

provide some arguments the first

argument which we need to provide here

is the port number so let me go ahead

and let me create another variable I

will call it port and to this let's

assign a port number let's say 3000

and let's pass this port variable as the

first argument to this listen method

all right and the second argument which

we need to pass here is a callback

function

for that I am using this Arrow function

syntax

now this callback function will be

executed as soon as the server starts

that means as soon as the server is

ready to receive requests so inside this

callback function let me go ahead and

let me log a console message saying that

server has started

all right

with this if I save the changes

let me go ahead and clear the console

first and let's now go ahead and let's

run this app.js file for that we can use

this command node space

app.js if I press enter you will see

that this message server has started has

been logged here that means now we have

started this node.js server

okay and where it is listening it is

listening to the Local Host and the port

number is 3000.

now what we want is we want to handle

some routes so for example let's say

whenever a user makes a request a get

request to the root URL we want to send

some response

so in the previous section we learned

how to handle routes

but here since we are using express.js

in express.js the routes are handled a

bit differently keep in mind that a

route consists of the URL plus the HTTP

method

let me put a comment here

so route equals HTTP method plus URL for

example let's say you are making a get

request to the root URL so the route

here is the HTTP method is get and the

URL is the root URL

now if you are making a post request to

the root URL then the route will be the

method is HTTP post and the URL is the

root URL okay so a route consists of the

HTTP method for example get post put

delete Etc and the URL

so let's say we want to define a route

where we want to handle the root URL

whenever a get request is made on that

root URL

so for that on this app on this app

object we have another method called get

so using this get method we can handle

get requests on the URL

the first argument of this get method is

the URL here we want to handle root URL

for that we can simply specify a slash

like this

now whenever a get request is made on

this root URL we want to do something

for that as the second argument to this

get method we can pass a callback

function and this callback function will

be called whenever a get request will be

made on this specified URL in this case

on this root URL

and this callback function is going to

receive two important arguments the

request object and the response object

and now from within this callback

function we can send some response

whenever a get request is made on this

root URL

and to send a response on the response

object which we are receiving as the

argument here we have a method called

send and using this send method we can

send an HTML response or a text response

for now let's simply send a text

response so here let's say hello from

Express server

okay

now before sending the response if you

also want to set the status code

on this response object we have another

method called status

okay now keep in mind that if you want

to set the status you need to set it

before sending the response okay here we

are doing the method chaining so before

the response is sent we want to set the

status of the response here let's say

the status is 200 all right so what is

happening here

whenever a get request will be made on

this root URL this callback function is

going to be executed and from within

this callback function we are sending a

response first we are setting its status

code to 200 and then we are sending a

response we are sending this text

response

let's verify this so here I will save

the changes let's stop the server by

pressing Ctrl C and let's restart the

server

let's go to the browser and here let's

type the URL so here we have to specify

the localhost which is

127.0.0.1 and the port number here is

3000 because that's the port number we

have specified and here you will see

this response hello from Express server

this is the same response which we are

sending when the user makes a get

request on this URL on the root URL

right we are sending this response Now

using this send method we can also send

HTML response so what I will do is I

will wrap this text within H4 element

okay let's save the changes again

let's stop the server by pressing Ctrl C

and let's restart the server and let's

go back to the browser

and now if I make a get request to this

root URL now we should receive some HTML

response so now you can see that this

text is bolded

all right now keep in mind that when we

use send method to send a response the

content type of the response is by

default set as text HTML

but let's say we want to send some Json

response

in that case we cannot use this send

method because as I mentioned when we

use send method the content type of the

response is set as Text slash HTML but

when we want to send a Json response in

that case the content type should be

application slash Json

so to send the Json response instead of

using send we need to use Json

all right and here we need to send some

Json response for that what I'm going to

do is I'm going to use a set of curly

braces there let's specify a property

maybe message and let's say message is

hello

world and let's also specify another

property maybe status and let's set it

to maybe 200. so now we want to send a

Json response so when we are using this

Json method in that case the content

type of the response will be set as

application slash Json and the Json

response will be sent let's see that

let's save the changes here let's stop

this server by pressing Ctrl C and let's

restart the server

let's go back to the browser and let's

make a request to this root URL and now

you will notice that here we are

receiving a Json response

let's go back to vs code

now here we are making a get request to

this root URL but what if we want to

make a post request

so if we make a post request to this

root URL in that case this route will

not be executed because this route will

only get executed when we make a get

request on the root URL

so to handle post request we will need

to Define another route

for that

on this app object we have another

method called post so using this post

method we can handle post requests here

we want to handle post request on this

root URL so there I will simply provide

slash

and then we can pass a callback function

here and this callback function will be

executed whenever a post request is made

on this root URL

and from within this callback function

we can write some logic which we want to

execute whenever a post request is made

on this root URL

okay so in this lecture we learned what

is express.js and why should we use

express.js instead of using vanilla

node.js because when we use express.js

it minimizes the number of lines of code

which we write

behind the scenes X Plus JS is already

using node.js but with express.js we

need to write a fewer lines of code

all right so in this section we are

going to learn all about express.js and

we are also going to create some apis

this is all from this lecture if you

have any questions then feel free to ask

it thank you for listening and have a

great day