Building a basic web application using Node.js

What is node and npm : Blog

• Node.js is a JavaScript runtime built on Chrome’s V8 JavaScript engine.
• Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.
• Npm is the package mangaer for node.js you can install any package on your machine from the repository.
• npx is node package execute, you can execute

package.json

• All npm packages contain a file, usually in the project root, called package.json - this file holds various metadata relevant to the project.
• This file is used to give information to npm that allows it to identify the project as well as handle the project's dependencies.
• It can also contain other metadata such as a project description, the version of the project, even configuration data - all of which can be vital to both npm and to the end users of the package.
• The package.json file is normally located at the root directory of a Node.js project.

Building a simple simple express application

1. Initialize a node application

    npm init

• You will find a menu Most of these details are pretty obvious, and for many of the prompts you can just select the defaults.

• Entry point is the javascript file that will be invoked when consumers of your module “require” it, this file will include the main logic for your module.

• After filling in the required information, a package.json file will be created with all the entered details

• Read about content inside package.json in detail in this blog: Blog

2. Install required dependencies

    npm install express --save

• This shall create a directory node_modules in your working directory.

3. Create a file app.js or name it as your entry point.

4. Start the server

//Requiring the express module that you installed
const express= require('express');
const app=express();

//Starting the server at PORT 3000
app.listen(3000, function(){
    console.log("Server Has Started");
});

What are "Ports"?

• At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service.
• A port is identified for each transport protocol and address combination by a 16-bit unsigned number, known as the port number.

HTTP Request methods GET, POST, PUT, DELETE

• You can read them about in depth here

GET Request

• Used to retrieve information
• Data is sent via query string
• Info is plainly visible in the URL
• Limited amount of data can be sent

POST Request

• Used to post data to the server
• Used to write/create/ update
• data is sent via request body not by query string
• Send any type of data

PUT and PATCH Request

• These two requests are used to update a resource on a server.
• Data is sent via request body
• The main difference between the PUT and PATCH method is that the PUT method uses the request URI to supply a modified version of the requested resource which replaces the original version of the resource, whereas the PATCH method supplies a set of instructions to modify the resource.

DELETE Request

• This request is used to delete a resource from a server.

CRUD Operations

Stand for create read, update and destroy.

5. Create a 'root' route

//Requiring the express module that you installed
const express= require('express');
const app=express();

//Creating making app to make a get request at route '/' (i.e localhost:xxxx/), function takes two arguments request (req) and response (res), we are returning a response saying hello world.

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

//Starting the server at PORT 3000
app.listen(3000, function(){
    console.log("Server Has Started");
});