JavaScript
	-high level language (now)
        -case senstive
        -not typesafe 
        -.js
        -initially it is function oriented , now it supports oops
        -is executed independently using Node
        -no main()
        -no explicit datatypes
        -it is a collection of objects
        -every statement is terminated with semicolon (;), but not mandatory

Price = 99;
console.log('welcome to javascript');
----------
Price = 99;
console.log(Price);
---------------------
Price = 99;
console.log('Price ' + Price);
--------------------------------
Price
console.log(Price);
ReferenceError: Price is not defined
---------------------------------------
Price = 99.29;
console.log(Price + '  ' + typeof(Price));
Price = 399;
console.log(Price + '  ' + typeof(Price));
Price = "JavaScript";
console.log(Price + '  ' + typeof(Price));
--------------------------------------------
Price = 399;
console.log(Price + '  ' + typeof(Price));
Price = "JavaScript";
console.log(Price + '  ' + typeof(Price));
Price = 'ashok it';
console.log(Price + '  ' + typeof(Price));
Price = 'a';
console.log(Price + '  ' + typeof(Price));
Price = 'admin#1234';
console.log(Price + '  ' + typeof(Price));
----------------------------------------
Price = 399;
console.log(Price + '  ' + typeof(Price));
Price = true;
console.log(Price + '  ' + typeof(Price));
Price = false;
console.log(Price + '  ' + typeof(Price));
------------------------------------------
Price = 399;
console.log(Price + '  ' + typeof(Price));
Price = "12/03/2025";
console.log(Price + '  ' + typeof(Price));
--------------------------------------------
Price = 399;
console.log(Price + '  ' + typeof(Price));
Price = "12/03/2025";
console.log(Price + '  ' + typeof(Price));
Price = null;
console.log(Price + '  ' + typeof(Price));
Price = undefined;
console.log(Price + '  ' + typeof(Price));
Price = [];
console.log(Price + '  ' + typeof(Price));
Price = {};
console.log(Price + '  ' + typeof(Price));
--------------------------------------------
Price = 399;
console.log(Price + '  ' + typeof(Price));
function Add(x,y)
{
    console.log(x+y);
}
Add(19,29);
Price = Add;
console.log(Price + '  ' + typeof(Price));
Price(10,20);
-----------------------------

datatypes - variables 
	-no need of datatypes to declare a variable.
        -use of variables with out declaring them is possible
	-implicit datatypes are available
        -datatype of a variable is decided based on the value assigned to it.
        -to use a variable, it should be declared or initialized.
        -value of a variable is allowed change
        -datatype of a variable can be changed

implicit or primitive datatypes
number => when variable is assigned with a numeric value of any type including floating point
string => when variable is assigned with a any type of content enclosed by double quotes or single quotes
boolean => when variable is assigned with true or false
undefined => when a variable is assigned with undefined
object  => when variable is assigned with null, [] , {}
function => when a variable is assigned with function name
-----------------------------------------------------------------
DAY - 2
--------
x = Number();
console.log(x);
output : 0
--------------------
x = Number(99);
console.log(x);
-------------------
x = Number(99);
console.log(x + '  ' + typeof(x));
99  number
--------------------------------
x = Number('javascript');
console.log(x + '  ' + typeof(x));
NaN  number
-------------------------------
x = Number(true);
console.log(x + '  ' + typeof(x));
1  number
--------------------------------
x = Number(false);
console.log(x + '  ' + typeof(x));
0  number
------------------------------
x = String();
console.log(x + '  ' + typeof(x));
  string
-----------------------------
x = String('Ashok It');
console.log(x + '  ' + typeof(x));
Ashok It  string
-----------------------------
x = String("Ashok It");
console.log(x + '  ' + typeof(x));
Ashok It  string
---------------------------------
x = String(true);
console.log(x + '  ' + typeof(x));
------------------------------
x = String(123456);
console.log(x + '  ' + typeof(x));
--------------------------------
data = 'testing';
x = String(data);
console.log(x + '  ' + typeof(x));
------------------------------------
data = 'testing';
x = String('data');
console.log(x + '  ' + typeof(x));
data  string
----------------------------------
x = Boolean();
console.log(x + '  ' + typeof(x));
----------------------------------
x = Boolean(true);
console.log(x + '  ' + typeof(x));
----------------------------------
x = Boolean(false);
console.log(x + '  ' + typeof(x));
-----------------------------------
x = Boolean(1);
console.log(x + '  ' + typeof(x));
----------------------------------
x = BigInt(99);
console.log(x + '  ' + typeof(x));
99  bigint
----------------------------------
x = Object();
console.log(x + '  ' + typeof(x));
---------------------------------
x = Object(99);
console.log(x + '  ' + typeof(x));
---------------------------------
x = Object('Arjun');
console.log(x + '  ' + typeof(x));
----------------------------------
x = Object(true);
console.log(x + '  ' + typeof(x));
---------------------------------
x = Object(null);
console.log(x + '  ' + typeof(x));
----------------------------------
x = Object(undefined);
console.log(x + '  ' + typeof(x));
---------------------------------
x = Date();
console.log(x + '  ' + typeof(x));
---------------------------------
Number()
String()
BigInt()
Boolean()
Object()
Date()
---------------------------------
declarion of variables 
	var let 

var Price  = 99;
console.log(Price  + '  ' + typeof(Price));
-----------------------------------------
let Price  = 99;
console.log(Price  + '  ' + typeof(Price));
-----------------------------------------
var Price
console.log(Price + '  ' + typeof(Price));
undefined  undefined
Note: a variable without value becomes undefined
----------------------------------------
Operators :
	Arithmetic Operators 
		+ - * / % *

var x = 10;
var y = 2;
var z = 3;
console.log(x + y);
console.log(x - y);
console.log(x * y);
console.log(x / y);
console.log(x % y);
console.log(x % z);
console.log(x ** y);
--------------------------------
var x = true;
var y = false;

console.log(x + y);
console.log(x - y);
console.log(x * y);
console.log(x / y);
------------------------------
var x = 10;
var y = 3;

console.log(x + y);
console.log(x - y);
console.log(x * y);
console.log(x / y);
13
7
30
3.3333333333333335
-------------------------
sign operators 
	+
        -
var x = +10;
var y = -6;
console.log(x + '   ' + y);
------------------------------
x = 10
y = 2
z = x + y;
x + y ---> arithmetic expression 
x y ----> operands
+ ------> operator
----------------------------
increment and decrement 
	++
        --
var x = 10;
var y = x;
console.log(x +   '   ' + y);
-------------------------------
var x = 10;
var y = ++x; //(pre) increment first - assign later
console.log(x +   '   ' + y);
----------------------------------
var x = 10;
var y = --x; //(pre) decrement first - assign later
console.log(x +   '   ' + y);
----------------------------------
var x = 10;
var y = x--; //(post) assign first -  decrement later
console.log(x +   '   ' + y);
----------------------------------
var x = 10;
var y = x++; //(post) assign first -  increment later
console.log(x +   '   ' + y);
----------------------------------
short-cut operators 
	+=
        -=
        *=
        /=
        %=

var x = 10;
x = x + 2; 
// x = 10 + 2;
// x = 12;
console.log(x);
-----------------------------
var x = 10;
//x = x + 2; 
x += 2;
console.log(x);
-----------------------------
var x = 10;
//x = x - 2; 
x -= 2;
console.log(x);
--------------------------
var x = 10;
//x = x * 2; 
x *= 2;
console.log(x);
-------------------------
var x = 10;
//x = x / 2; 
x /= 2;
console.log(x);
-------------------------
var x = 10;
//x = x % 2; 
x %= 2;
console.log(x);
-------------------------
relative operators or comparison operators 
	>
        <
        >=
        <=
        ==
        ===
        !=
Note: any valid relative expression always returns boolean value. so these are called boolean expressions.
var x = 10;
var y = 2;
var z = 10;
console.log(x > y); // 10 > 2--> true
console.log(x > z); // 10 > 10 --> false
console.log(x>=z); // 10 >= 10 --> true
console.log(x < y); // 10 < 2 ---> false
console.log(x < z); // 10 < 10 --> false
console.log(x <= z); // 10 <= 10 ---> true
console.log(x == y); // 10 == 2 ---> false
console.log(x == z); // 10 == 10 ---> true
console.log(x != y); // 10 != 2 ---> true
console.log(x != z); // 10 != 10 ---> false
-----------------------------------------------
var x = 10;
var y = 10;
var z = '10';
var a = '99';
var b = 'arjun';
console.log(x + '  ' + y + '  '+ typeof(x) + '  ' + typeof(y) + ' ' + (x == y));
console.log(x + '  ' + z + '  '+ typeof(x) + '  ' + typeof(z) + ' ' + (x == z));
console.log(x + '  ' + a + '  '+ typeof(x) + '  ' + typeof(a) + ' ' + (x == a));
console.log(x + '  ' + b + '  '+ typeof(x) + '  ' + typeof(b) + ' ' + (x == b));
console.log(x + '  ' + z + '  '+ typeof(x) + '  ' + typeof(z) + ' ' + (x === z));
-----------------------------------------------------------------------------------
logical operators 
	&&
	||
	!

	&&   and
	||   or
         
        -used to join multiple conditions together as one unit
        &&
           -returns true, when all the joined condition's result is true
           -cond1 && cond2 && cond3 && ......&& condN
           -if any one condition's result is false, no need to evaluate the remaining conditions

        || or
              - returns true, when atleast one condition's result is true
              -cond1 || cond2 || cond3 || ......|| condN
              -if any one condition's result is true, no need to evaluate the remaining conditions
         
	! - returns opposite of the condition's result

console.log(true && true);
console.log(true && false);
console.log(false && true);
console.log(false && false);
true
false
false
false
------------------------------
console.log(true || true);
console.log(true || false);
console.log(false || true);
console.log(false || false);
true
true 
true 
false
-------------------------------
console.log(true );
console.log(false);
console.log(!true);
console.log(!false);
true
false
false
true 
------------------------------
console.log(!1);
console.log(!0);
------------------------------
ternary operator
	? :
-----------------------------
control structures :
	-used to control the flow of execution among the statements of the program.
        -selection of one or more statements either to execute or to skip from execution based on a condition.

console.log('Good Monring');
console.log('Good AfterNoon');
console.log('Good Evening');

cs are two types
	-non-iterative cs
	-iterative cs

-non-iterative cs
	1.if
        	a.simple if   - only one option
                  if(condition)
                  {
                        // executes when the condition's result is true
			// some logic 
                  }


 		b.if...else    - two options
                  if(condition)
                  {
			// executes when the condition's result is true
			// some logic 
                  }
                  else
                  {
                       // executes when the condition's result is false
			// some logic  
                  }

                 c.if..else if...else..if...else (ladder if)
                 if(condition1)
                  {
			// executes when the condition's result is true
			// some logic 
                  }
                  else if(condition2)
                  {
                       // executes when the condition's result is true
			// some logic  
                  }
                  else if(condition3)
                  {
                      // executes when the condition's result is true
			// some logic  
		  }
                  -----------------------
                  -----------------------
                  -----------------------
                  [else
                  {
                      // executes when all the condition's results are false
                      // logic
                  }]


                 4.switch   - used to check one value against multiple options

                   switch(variable/exp/value)
                   {
                        case value1:
				// logic
                                break;
			case value2:
			        // logic
                                break;
                        case value3:
                                // logic
                                break;
                        ---------------
                        ---------------
                        ---------------
                        ---------------
                        default:
				// executes when no case value is matched
                                break;														
                   }
-------------------------------------
x = 10;
y = 10;
if(x < y)
{
    console.log(x + ' is less than  ' + y);
}
else if(x > y)
{
    console.log(x + ' is greater than ' + y);
}
else 
{
    console.log(x + ' is equal to ' + y);
}

--------------------------------------------
x = 10;
y = 10;
if(x < y)
{
    console.log(x + ' is less than  ' + y);
}
else if(x > y)
{
    console.log(x + ' is greater than ' + y);
}
else if(x == y)
{
    console.log(x + ' is equal to ' + y);
}
--------------------------------------------
userType ='visitor'; // use different values 
switch(userType)
{
    case 'admin':  // if(userType == 'admin')
        console.log('load admin page');
        break;
    case 'employee':
        console.log('load employee page');
        break;
    case 'customer':
        console.log('load customer page');
        break;
    case 'supplier':
        console.log('load supplier page');
        break;
    case 'guest':
        console.log('load guest page');
        break;
    default:
        console.log('invalid user type...check once');
        break;
    
}
-----------------------------------------------------------
x = 35;
switch(true) // true
{
    case x>=90: // true == false
        console.log('A+');
        break;
    case x>=80: // true == false
        console.log('A');
        break;
    case x>=70: // true == false
        console.log('B');
        break;
    case x>=60: // true == false
        console.log('C');
        break;
    case x>=50: // true == false
        console.log('D');
        break;
    case x>=35: // true == true
        console.log('E');
        break;
    default:
        console.log('F');
        break;

}
-------------------------------------------
 iterative control structures
   a.while
   b.do..while
   c.for
  	-used to execute one or more statements again and again based on a condition
	-avoids duplication of code
	-supports re-usability