Java script c-2 variables

kavin K — Sat, 22 Aug 2026 03:51:49 +0000

i)let
ii)const
iii)var

Let,var -almost same
let-It works in {} only
var-It works in globally.outoff {}

const-we cannot change the value.
Eg.amazon order limit.

Program:

clickme
</button)

addnumbers - function name
clickme - button name

Program:
let a=100
function addnumbers()
console.log(a)

Op:
100

var name="kavin"
var name="Praveen"
var name="naresh"
console.log(name)

Op:
naresh
console.log(name) access immediate reference.

*we can't initiate one or more variable with same name in let and const.But we do that in 'var'.

Demerits of var:

i)initialzes more reference values in same name. It has more chance to create bug.

function addNumbers(){
var a=10;
{
var a=15;
}
console.log(a);
}
console.log(a);----->
Op:
a is not defined
Var-It is afunction scoping. It works in within function only {}

If stop the the last "console.log(a);" we will get the op of value is "15".

let vs var:
we can access the value out of scoping{} in var.

Eg:
{
var a=15;
}
console.log(a);
Op:
15

Hosting:
function addnumbers(){
console.log(a);
var a=10;
{
var a=15;
}
console.log(a);
}
Op:
undefined
15

if we create var, it initially move to the top and it assigned to undefined.

Responsive Design

kavin K — Fri, 14 Aug 2026 00:55:22 +0000

d12;
*Responsive design:
It is used for good look websites. Automatically adjusting their layout, colour.
i)Use technologies:
Flexible grids
Responsive images
Css media queries

Eg: We give one colour(yellow) for words during code time.. But chanage the colour(green) during printed time.

Max width Vs Min width:
Max width: Laptop to Mobile
Min width: Mobile to Laptop

Both Min width and Max width:

Syntax:@media screen and (min-width:500px) and (max-width:900px)

icon tag:
It is just small one image
It is operate by check box(#input type)

Alternate method:use button

limitations:if we use button, we will use java script language.

why we use label?

.......

Grid:line setup(21.10)
include:
#img
#header

#paragraph

Box sizing:
i)border box
ii)content box

JAVA SCRIPT:
Java script is a versatile, high level programming language used primarily to create interactive and dynamic content on the web.
*javascript run in web page.

interactive- man discussed with computer
dynamiccontent- change the web page(eg.click the icon button it expand and show Home,About, login page etc.)

*It allows websites to respond instantly(eg:login page) to user actions without needing to reload the entire page.

*JavaScript is a single-threaded language that executes one task at a time.(Eg:first complete instagram, airbnb, youtube)5.29
*it is an interpreted language which means it execudes the code line by line.

*The data type of the variable is decided at run-time in javascript that's why it is called dynamically typed.
run-time:code run aagura time.
dynamically typed:It is need not variable. it take automatically(variable-int,string etc)

JIT Compiler:
Just In Time
It converts the code Javascript(English) to 0's and 1's.

compiler:
(compiler take all code then it convert (English to Binary code)
In javascript read all the code at a time. Eg:Read someone Rich dad poor dad book after complete book he say all the content.

compilation:
The process that invloves the translation of Javascript code into machine code occurs using compilation interpretation.
In compilation the entire source code is converted into machine code at once and written into a binary file to be executed by the computer.
(binary file-.class file)
sourcecode--binarycode--storebinarycodefile(.class file).this process is presents in Java. But this process only not present in javascript.

sourcecode-------------machinecode-----------Hello world
(compilation)(binary file)(execution)

Interpretation:
source code-------------------------------------Hello world
Execution
In contrast, during interpretation, the interpreter goes through the source code and interprets it line by line, executing each line as it encounters it.

JIT compiler:
Javascript combines both compilation and interpretation.
This is called JIT.compilation. This method compiles the entire code into machine code all once and executes it.

source code---------Machine code---------Hello world
compilation | executuion
|
not create .class file in javascript. it creates java only.

25.50*********************
1.Interpreter:
An interpreter runs instructions directly from the programming language without changing them into machine code.

2.Compiler:
A compiler changes the entire program into object code(or binary code) and saves it. This code can then be run by the machine.

JIT compiler = Interpreter+compiler

28.54

what is variable?
It is helps store data.
To access data.
It is like container.

html

kavin K — Tue, 04 Aug 2026 17:31:40 +0000

html is hyper text language.

DEV Community: kavin K