Node.js and Typescript

Banuprakash C

Full Stack Architect,

Co-founder Lucida Technologies Pvt Ltd.,

Corporate Trainer,

Email: banuprakashc@yahoo.co.in

https://www.linkedin.com/in/banu-prakash-50416019/

https://github.com/BanuPrakash/NODE

---

Softwares Required:

1. Visual Studio Code. [https://code.visualstudio.com/download]
2. Chrome Web Browser
3. NodeJS Latest LTS Version: 16.x.x [https://nodejs.org/en/download/]

================================

JS ==> JS engine [ V8 { Google ==> Chrome, NodeJS}, SpiderMonkey [ FireFox, Adobe], Chkra, Nashorn, ...]

NodeJS

• Platform built on V8 engine runtime
• event-driven [Thread ], non-blocking I/O model [NIO]

libuv is a multi-platform C library that provides support for asynchronous I/O based on event loops. It is primarily designed for use in Node.js but it is also used by other software projects.

https://github.com/nodejs/node

event loop psuedocode

//myFile.js

const microTask = []; // PromiseAPI, async await, nextTick()

const pendingTimers = []; // macrotask ==> setTimeout, setInterval, setImmediate const pendingOsTasks = []; // macrotask const pendingOperations = []; // macrotask

function shouldContinue() { return pendingTimers.length || pendingOsTasks || pendingOperations.length .. }

// Running Thread while(shouldContinue()) { // is stack empty // 1 check all microTasks and empty it ==> push them to Stack // 2 check and empty all pendingTimers ==> push them to Stack // 3 pending OS tasks ==> Socket related, I/O callbacks ==> read chunk of data from file ==> push them to Stack // 4 Pending Operations ==> close of connections , etc ==> push them to Stack // pause execution }

Tick ==> one iteration of while()

======================

myfile.js

console.log("Hello!!!");

setTimeout(function one() { console.log("t1"); }, 0);

setTimeout(function two() { console.log("t2"); }, 0);

Promise.resolve().then(function p1() { console.log("p1"); });

Promise.resolve().then(function p2() { console.log("p2"); });

console.log("Bye!!!");

=====================

https://www.jsv9000.app/

=====================================

function logA() {..} function logB() {..} function logC() {..} function logD() {..} function logE() {..} function logF() {..} function logG() {..}

logA();

setTimeout(logG, 0);

Promise.resolve() .then(logB) .then(setTimeout(logC)) .then(logD) .then(logE);

setTimeout(logF);

==================================

process.nextTick()

Every time the event loop takes a full trip we call it as tick.

// microtask process.nextTick(function task() { // do something });

==> function executes at the end of current tick.

setTimeout(function timed() {

}, 0);

===========================================

NodeJS V8 Memory Structure

• ResidentSet

• Code Segment ==> JIT compiler compiles code blocks

• Heap

  1. New Generation [ SemiSpace 1, Semispace] ==> In Java ==> Surviour state 1 and Surviour state 2
  2. Old Generation

• Stack

• Large Objects [Code, MMap]

C#, JS and Java or any technology which uses Virtual machine doesn't allow pointers

node --min_semi_space_size(intial) --max_old_space_size(max) --stack-size(size) server.js

===================================================================

nodeJs provides built-in modules crypto, fs, http, path, repl, ...

Module System:

1. IIFE ==> Immediately invoke function expression

let ShoppingModule = (function() { let data = 100; function doTask() {

}
return {
	doTask
}

})();

let paymentModule = (function() { let data = 999; let done = false; function doTask() {

}
return {
	done,
	data,
	doTask
}

})();

ShoppingModule.data ==> 100 // not visible paymentModule.data ==> 999

2. CommonJS module system ==> default module system in NodeJS

   compute.js

   module.exports.add = function(){ }

   function sub() {

   }

   other.js

   let compute = require('./compute');

   can access compute.add() but not compute.sub()

3. ESM ==> ES 6 module system

export const add = function() {}

other.js

import {add} from './compute';

4. AMD
5. System
6. UMD ==> wrapper for different module system to dynamically decide which module system has to be used

• NodeJS Threads concept

• NodeJS Async Operations Network related operations doesn't use libuv Threads

==================================================

node.js Event Emitter

=================

• fs sync
• fs callback
• fs stream based

Where can i use NodeJS?

1. Real time application
2. Streaming API ==> Netflix Squid Game chunk of data has to pushed to client; client buffers
3. Traditional Web application ==> server rendered pages
4. build RESTful Web services
5. GraphQL services

==============

npm i -g learnyounode

learnyounode

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