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04.Web Server Backend.md

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Basic stuff:

Field Sample Description
Scheme http The protocol used.
Domain name https://martino.im The location of the resource.
Port :80 The "gate" used to access the resource.
Path //path/to/myfile.html The path to the resource we are looking for.
Parameters ?key1=value1&key2=value2 Parameters used to manage the operations for the resource.
Anchor #SomewherelnTheDocument A bookmark to a location in the webpage.

Possible answers:

Code Description Actual Meaning (Server's perspective)
2xx The action was successfully received, understood and accepted. Everything is okay!
3xx The client must perform additional actions to fulfil the request. I know what you want, but it is not there, anymore. Let me tell you the new location...
4xx The request is syntactically incorrect or cannot be fulfilled I have actually no idea of what you want.
5xx The server has failed to fulfil an apparently valid request. I just decided to blow up and stop, working.

The most commonly utilized web servers are:

  • Apache
  • NGINX
  • Microsoft IIS
  • LiteSpeed Web Server

Static files and dynamic files

Static files are content that is already generated and complete and, when served, doesn’t require any additional information/data. HTML, JS, CSS, images are example of static files.

There are several reasons why dynamic files are crucial in web development:

  • Efficiency and Scalability: Scale web applications as demand grows is easier since the server can generate pages and content as needed, rather than relying on static files that must be manually updated.
  • Customization and Interactivity: generating pages on-the-fly, dynamic files make it possible to personalize web pages based on the individual user's preferences and behaviors. This is probably the most important feature of a dynamic website.

JSON

  • JSON stands for JavaScript Object Notation.
  • It is used as a data transfer convention over the internet.
  • JSON is written in the format of a JavaScript Object/Array.

API and REST

APIs enable abstraction of the internal workings of a system, providing only the relevant parts to the programmer. An API is categorized as REST API if it adheres to the following principles:

  • Client-Server paradigm
  • Stateless
  • Uniform interface
  • Cacheability
  • Layered system

from https://api-first-world.com/

NGINX and Apache are good for static file serving and load balancing. In 2009, JavaScript was recognized as an actual programming language and not just a browser tool.

NodeJS and modules

Node.js is an environment for running JavaScript code outside a web browser, using the V8 engine. Modules are officially used to package and import code inside other modules. All modules used are saved in the node_modules folder within the project. Endpoints are the main part of the web server, and each one corresponds to a functionality offered by the server.

It's very important to not upload node_modules folder since using npm install inside the folder any module is automatically fetched with npm.

import express from 'express';
const app = express();

//Each endpoint corresponds to a functionality that we offer

// Simple endpoint that send a message when called
    app.get('/', (req, res) => {
        res.send("Everything's OK!").status(200);
    })

// Endpoint that saves a value in the database
    app.post('/db', async (req, res) => {
        // The data is stored in the body of the request
        let data = req.body;
        
        // try/catch is a construct that allows to try to do something. 
        // If it fails, the operation inside the catch are executed
        try {
            // Trying to save data in the DB
            await model.DB.create(data);
            res.status(200).send()
        }
        catch {
            // Send back error in case something went wrong (for example, empty fields)
            res.status(400).send()
        }    
    })
    
// The server listen port 3000
app.listen(3000);
Method Function Description
GET app.get(...) Requests that usually want to retrieve data.
POST app.post (...) Requests that want to create new data.
PUT app.put(...) Requests that want to modify existing data.
DELETE app.delete (...) Requests that want to delete existing data

Postman is a website that can be used for testing servers. It is basically used to simplify the creation of APIs.

Random notes

Nodejs Express

NodeJS project

When you land into a project where there is package.json you can install everything ... using npm install .

Remember to not commit node_modules.

npm run build