Node JS

Node JS Installer (opens in a new tab)
Node JS Documentation (opens in a new tab)
npm init command is used to initial a package.json file.
node <filename>.js command is used to run a javascript file using NodeJS

To use NodeJS in web browser, in index.html add <script src=""></script>

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta
      name="viewport"
      content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0"
    />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
  </head>
  <body>
    <script src="./index.js"></script>
  </body>
</html>

Node Modules

File Based
Build In
Third Party

1. File Based

`index.js` file

module.exports = {a, b} is used to export the selected modules, for re-use of code.

// console.log("Hello World")
 
const a = 100;
 
const b = {
  average: (a, b) => {
    console.log((a + b) / 2);
  },
  percent: (a, b) => {
    console.log(a / b / 100);
  },
};
 
module.exports = { a, b };

`app.js` file

require() is a built-in function to include external modules that exist in separate files

const { a, b } = require("./index.js");
 
console.log(a);
 
b.average(10, 20);
b.percent(10, 20);

2. Build In

fs (File System Module) allows us to work with files present locally in the system.
path module allows us to work with directories and file paths.
os (Operation System module) provides information about the computer's operating system.
events helps trigger an action / event on a computer

Reading Files

reading value from sample.txt file
```
Hello NodeJS !
```

Asynchronous Functions

The heavy tasks are worked in background meanwhile, rest of the code is executed once
heavy task is executed the Call-Back function is called Non-Blocking Nature ✅

asynchronouse.js file

const fs = require("fs");
 
// console.log(fs);
 
fs.readFile("./sample.txt", "utf-8", (error, data) => {
  if (error) {
    throw error;
  }
  console.log(data);
});
 
console.log("I am First");

Output

I am First
Hello NodeJS !
 
Process finished with exit code 0

console.log("I am First") is executed first because fs.readFile() is Asynchronous function

Synchronous Function

Runs file line by line, waits of complete execution current line complete
Makes JavaScript Code Slow and is called Blocking Nature ❌

synchronous.js file

const fs = require("fs");
 
const a = fs.readFileSync("./sample.txt", "utf-8");
 
console.log(a);
console.log("I am first");

Output

Hello NodeJS !
I am first
 
Process finished with exit code 0

Writing Files

Asynchronous Function

asynchronous.js file

const fs = require("fs");
 
const a = "This is output";
 
fs.writeFile("./sample.txt", a, () => {
  console.log("Written");
});
 
console.log("I am First");

Output

I am First
Written
 
Process finished with exit code 0

sample.txt file
```
This is output
```

Synchronous Function

synchronous.js file

const fs = require("fs");
 
const a = "This is output";
 
fs.writeFileSync("./sample.txt", a);
 
console.log("Written");
console.log("I am First");

Output

Written
I am First
 
Process finished with exit code 0

sample.txt file
```
This is output
```

3. Third Party

Third Party modules are modules which are written by some else, and are used in a project.
Examples: Express, Gulp, React, Mongoose, Async

Using `pokemon` module

installing pokemon module by using npm install pokemon

╭─ npm install pokemon
 
added 3 packages, and audited 5 packages in 5s
 
2 packages are looking for funding
  run `npm fund` for details

index.js file

const pokemon = require("pokemon");
 
console.log(pokemon.all());

Output

  [
  'Bulbasaur',  'Ivysaur',    'Venusaur',   'Charmander', 'Charmeleon',
  'Charizard',  'Squirtle',   'Wartortle',  'Blastoise',  'Caterpie',
  'Metapod',    'Butterfree', 'Weedle',     'Kakuna',     'Beedrill',
  'Pidgey',     'Pidgeotto',  'Pidgeot',    'Rattata',    'Raticate',
  'Spearow',    'Fearow',     'Ekans',      'Arbok',      'Pikachu',
  'Raichu',     'Sandshrew',  'Sandslash',  'Nidoran♀',   'Nidorina',
  ... 865 more items
]
 
Process finished with exit code 0

Using `nodemon` module

nodemon module is a simple monitor script for use during development of a Node.js app

installing nodemon globally, by npm install nodemon -g

  ╭─ npm install nodemon -g
 
added 32 packages in 2s
 
3 packages are looking for funding
  run `npm fund` for details

Creating a NodeJS server

index.js file

const http = require("http");
const PORT = 4000;
const HOST = "localhost";
 
const server = http.createServer((request, response) => {
  response.end("Working...");
});
 
server.listen(PORT, HOST, () => {
  console.log(`Server is working on http://${HOST}:${PORT}`);
});

Terminal

Server is working on http://localhost:4000

Localhost : 4000

Routing using NodeJS Server

index.html file

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta
      name="viewport"
      content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0"
    />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
    <style>
      html {
        background-color: #1e2537;
        color: white;
        height: 100vh;
        font-family: Arial;
      }
    </style>
  </head>
  <body>
    <div class="home">
      <h1>Home Section</h1>
    </div>
  </body>
</html>

route.js file

const http = require("http");
const fs = require("fs");
 
const PORT = 4000;
const HOST = "localhost";
 
const home = fs.readFileSync("./index.html", "utf-8");
 
const server = http.createServer((request, response) => {
  if (request.url === "/") {
    response.end(home);
  } else if (request.url === "/about") {
    response.end("<h1 style='font-family: Arial'>About Page</h1>");
  } else {
    response.end(
      "<h1 style='font-family: Arial; color: #FC6E68'>404 Page Not Found</h1>"
    );
  }
});
 
server.listen(PORT, HOST, () => {
  console.log(`Server is working on http://${HOST}:${PORT}`);
});

LocalHost: 4000

Deploying the NodeJS server

npm start command to work, add "start": node ./server/route.js in "scripts" : {} object in package.json file

{
  "name": "00-basics",
  "version": "1.0.0",
  "description": "learning nodeJS",
  "main": "modules/file-based/index.js",
  "scripts": {
    "start": "node ./server/index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "prettier": "2.8.7"
  },
  "dependencies": {
    "pokemon": "^2.3.4"
  }
}

Output

╭─ npm start
 
> 00-basics@1.0.0 start
> node ./server/index.js
 
Server is working on http://localhost:4000

Mern Stack 2. Express Basics

Node JS

Node Modules

1. File Based

index.js file

app.js file

2. Build In

Reading Files

Asynchronous Functions

Synchronous Function

Writing Files

Asynchronous Function

Synchronous Function

3. Third Party

Using pokemon module

Using nodemon module

Creating a NodeJS server

Routing using NodeJS Server

Deploying the NodeJS server

`index.js` file

`app.js` file

Using `pokemon` module

Using `nodemon` module