notes.md

Week 04 Day 4

Topics

• Intro to JavaScript
  • History
  • JS data types
  • JS operators

Intro

• Scripting language vs programming language
• why do we need to learn programming language?
  • how js came to be one of the core tech of the www
• basically web concept -- file stored in another computer are fetched, then served into another computer

History

• netscape navigator, early 1995
• it was all static, there's was no user interaction, it was bland and bording
• used primarily for acadameic purposes

Advent of Mocha

• as web become popular there was a new need of interactive stuff
• which required a small scripting lang that could introduce interactivity of web page
• java was pretty famous back then
  • but it was kind of difficult plus it was closed community language
• so they could not use java for web purposes
• this lent to advent of MOCHA scripting lang

A language for Web Browsers

• scheme was dev by Brenden Eich (father of JS)
• 90s java was ruling, there was a lot of pressure on Mocha dev
  • they wanted to come up with working prototype of Mocha
  • they also wanted to take advantage of java's popularity for marketing reasons
• java was resevered to be a corporate friendly lang

Releases of JavaScript

• dec, 1995, netscape launched Mocha, soon renamed as LiveScript
• IE was bubbling in dev labs at Microsoft, they were focusing more compilation/web browser part
• nov 1996, v2 of Mocha, renamed as LiveScript
• now came a new web browser netscape navigator (grandpa of firefox) which had very first JavaScript
  • this was well received amongst web development community
  • there were still a lots of bugs which were polished in v3

Dawn of ECMAScript

• there was a need for some standards to write JS for easy maintenance
• ECMA was formed 1961 which was concerned with standardisation of information
• due to trademark reasons, JS was not the accepted name, it's offically called "ECMAScript"
• first ver of ECMAScript came live during 1997 along with Netscape 4
• critical features were missing, ECMA script v2 came in 1998
• following es2 with minor updates
• ability to connect website was a reality after AJAX was born
• netscape and IE5 supported it

ECMAScript 6

• most accepted upgrage of JS, still in 2020, there are still some features not fully supported by web browsers
• Transpilers like babel compiles code into backward JS for more support across devices

Future of JS

• web assembly
• running native assembly lang on to the web, which is low level hence much faster

JavaScript

• console will read loaded js file from web browser and can be used to playaround

Print

1. console.log()

   console.log("console logged");

2. document.write()

   document.write("hello, world!"); // non-blocking output

3. alert()

   alert("this is alert!"); // blocking output

Taking I/T from user

• using prompt

   prompt("enter name ");

Variables

1. Declaration (create)
2. Initialization (store)

• Example

   var name = "rahul choudhary"; // doing declaration and init together

Data types

1. undefined - bucket with garbage value
2. null - empty container, use when sure var is going to be empty, if not meaningful
3. Arrays
4. Objects
5. Boolean - true(1) or false(0)
6. Number
7. String - "Rahul Choudhary"
8. BigInt
9. Symbol
10. Object

JS operators

Arithmetic operators

+ 	 Addition
- 	 Subtraction
* 	 Multiplication
** 	 Exponentiation (ES2016)
/ 	 Division
% 	 Modulus (Division Remainder)
++ 	 Increment
-- 	 Decrement

Logical operators

||	 or (either)
&&   and (both)
!    not (none)

Comparision operators

===  strictly equal
==   normal equal
<=   less than or equal
>=   greater than or equal
!==  strict not equal
!=   not equal

Ternary operators

• to be continued