Intro to backend (Using Javascript)

Introduction

• So far all the Javascript, HTML and CSS we have learnt is part of front end, i.e the part the user interacts with. But to make a fully working web app we need what we call a "backend". It has three parts - Database, Server and Application.

• Database is the storage part where we can store large amounts of data for a long time.

• A server is basically a computer that is ready all the time to serve you listen to user requests and reply with html and css that the browser can use to render a web page.

• Application is the logic that decides wt we do with certain types of requests.

• We can write back end code in pretty much any language including ruby, php, python and JavaScript.

• Here I will be using Javascript with node js and express js.

Node JS

• JavaScript is made to be a language that runs in a browser, but for us to use it as the backend we need it to run on the server.

• Node JS uses the V8 chrome engine to basically create an environment to run JavaScript outside the browser.

• We will have to install node js on the server meant to run the code, we can use npm (a packet manager) to install dependencies/packages or frameworks as needed for the code.

• We'll learn basics of node JS using a simple project - a QR code generator.

QR-Code Generator

import inquirer from "inquirer";
import qr from "qr-image";
import fs from "fs";

inquirer.prompt([
    {
        name: 'URL',
        message: 'What would you like to create a QR to?',
    }])
    .then(function(answer){
        const url=answer.URL;

        var qr_svg = qr.image(url);
        qr_svg.pipe(fs.createWriteStream('qr.png'));

        fs.writeFile("URL.txt",url,(err) => {
            if (err) throw err;
            console.log("The file has been saved!");
          });

    });

• We will be using three packages - inquirer, qr-image and fs

• First we use the inquirer to create a prompt to take a user input (The URL to create the QR code for).

• You then extract the URL from the input and create a qr image with it and save this image into the file system.

• We then take the user input and save it as a text file.

• you can then scan the qr to do all your dirty shenanigans.

Conclusion

• So today we learnt what node JS is and how to use it.

• Any and all advice is accepted i really do want to learn more : )

github -> https://github.com/P-M-Manmohan

LinkedIn -> https://www.linkedin.com/in/manmohan-p-m-78618323a/