I believe you didn't know this about

JavaScript

Joseph Khan

25 Sep, 2019 | Dubai

Weird history, some fun facts, and concepts around

JavaScript 

About Me..

Joseph Khan

Web Specialist @ Tajawal

Author of Adobe Edge Inspect Starter

Technical Reviewer of Sencha Touch Cookbook

https://josephkhan.me

History Facts

Weird JS

Some numbers

Future

Try

Gmail (2004) and

Google Maps (2005)

2015 - ES6 released

2017 - ES8 released

2018 - ES9 released

2019 - ES10 released

JavaScript has grown from this

to this...

Did you know that?

Brendan Eich 

Wrote JavaScript in 10 days

Told to write scheme for Netscape

Was aware of 23 == "23" anomaly

Guy Steele

He helped Brendan standardize JavaScript 

Co-creator of Scheme  

‘Don’t worry about it. There are Lisps that have five kinds of equals operators. We’ll just add another one.'​

The first standard version (ES1) missed try catch, reg exp, strict equality.

Was added in ES3

JavaScript had a sister/brother "ActionScript" 

Used by Flash & Flex

NodeJs was't the first server side JS

1995 - Netscape Enterprise Server

1996 - MS IIS Web Server Server

SpiderMonkey

V8

JavaScript interpreters are themselves written in C++

You can specify defer or async in your <script /> tag (head) to avoid render blocking issues

<script async src="script.js"></script>
<script defer src="script.js"></script>

null is an Object

typeof null === 'object' //true


null instanceOf Object; //false

NaN is a Number

typeof NaN === 'number' //true


NaN === NaN; //false

null & undefined

1 + null; //1

1 + undefined; //NaN


typeof null; //'object'
typeof undefined; 'undefined';

Has data types..

var n = 12;
typeof n; //"number"
n instanceof Object; //false

var s = "hello";
typeof s; //"string"

var b = true;
typeof b; //"boolean"

typeof undefined; //"undefined"

typeof null; //"object"

var sym = Symbol('a');
typeof sym; //"symbol"
var arr = [];
typeof arr; //"object"
arr instanceof Object; //true

var f = function() {};
typeof f; //"function"
f instanceof Object; //true

Primitive types

Objects

JS has a void operator

Has comma operator

void 0; //returns undefined
void(1); //returns undefined

void 'hello'; //undefined
void {}; //undefined
void []; //undefined

void myFunction(); 
void(myFunction());
let result = expression1, expression2,... expressionN

const getSquare = x => (console.log (x), x * x)

JS is Object Oriented

Prototype chain and inheritance

You can augment built in Higher Order Objects

String.prototype.reverse = function() {
  return this.split('').reverse().join('');
}

var s = "hello";
s.reverse(); //"olleh"

Global variables

function foo() {
    x = 10; // Whoops
}
foo();
console.log(x); // 10

window is not part of JavaScript

window.dumpMyGlobal = 'Hello There!';

setTimeout() parameters

setTimeout(console.log, 1000, 'Hello World!', 'And Mars!');

Arrays

var arr = [1,2,3,4];

typeof arr; //'object'

arr instanceof Array; //true
arr instanceof Object; //true
arr.constructor === Array; //true

arr.constructor.name === 'Array'; //true

Named Constructor

//2 ways to create a number
var n1 = 12;
var n2 = new Number(12);

typeof n1 === 'number'; //true
typeof n2 === 'object'; //true

n1 + 2; //14
n2 + 2; //14

JSFuck

Subset of JavaScript 

Code using 6 chars - [ , ] , ( , ) , ! and +

JavaScript is a..

high-level

single-threaded

gargbage-collected

interpreted

prototype-based

multi-paradigm language

dynamic

non blocking event loop

JavaScript is

single-threaded - means it can do only one thing at a time

asynchronous - means it can do more than one thing at a time

How the runtime works

console.log('A');


console.log('B');


console.log('C');

Output

console.log('A')
console.log('B')
console.log('C')

A

B

C

Call Stack

console.log('A');


blockingTask();


console.log('C');

Output

console.log('A')
blockingTask()

A

Call Stack

Asynchronous Callbacks

How does it achieve concurrency?

console.log('A');


setTimeout(function() {
  console.log('B');
}, 5000);


console.log('C');

Output

console.log('C')

Call Stack

Web API's

Callback queue

setTimeout(cb, time)
callback
callback
callback
callback

Event Loop

callback
console.log('B')
callback

JS is the most run language on the planet

You’re coding on GitHub in hundreds of programming languages, but JavaScript still has the most contributors in public and private repositories, organizations of all sizes, and every region of the world.

From browsers to mobile phones, from tablets to tabletops, from industrial automation to the tiniest microcontrollers

JavaScript in Space ...

Nanosatellite which uses NodeJS platform was launched into space on Nov 29, 2018 from India

Reaktor Hello World Satellite

JavaScript of Things, JOT

Problem

Guess the answer

function funky(o) {
  o = null;
}

var x = [];

funky(x);

alert(x);


What is x ??
  • null
  • [ ]
  • undefined
  • throw

<thank-you />

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I believe you didn't know this about JavaScript

By Joseph K

I believe you didn't know this about JavaScript

Weird history, some fun facts, and concepts around JavaScript

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