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 
        -write once - use many times.

declaration and initialization of looping variable
condition on looping variable's value
change in the looping variable's value
---------------
var i = 1;
while(i<=6) // condition checking is at the starting /entry point 
{
    console.log(i + "  inside the while loop " + (i<=6))
    i = i +1;
}
console.log(i + "  outside the while loop " + (i<=6))
1  inside the while loop true
2  inside the while loop true  
3  inside the while loop true  
4  inside the while loop true  
5  inside the while loop true  
6  inside the while loop true  
7  outside the while loop false
-----------------------------------
var i = 1;
do
{
    console.log(i + "  inside the do-while loop " + (i<=6));
    i = i +1;
}while(i<=6)
console.log(i + "  outside the do-while loop " + (i<=6));
------------------------------------------------------------
var i = 11;
do
{
    console.log(i + "  inside the do-while loop " + (i<=6));
    i = i +1;
}while(i<=6)
console.log(i + "  outside the do-while loop " + (i<=6));
11  inside the do-while loop false
12  outside the do-while loop false
Note: do-while executes at-least once even the condition's result is false.
-------------------------------------------
var i = 11;
while(i<=6) // condition checking is at the starting /entry point 
{
    console.log(i + "  inside the while loop " + (i<=6))
    i = i +1;
}
console.log(i + "  outside the while loop " + (i<=6))
11  outside the while loop false
--------------------------------------------------
for
---
var i;
for(i=1;i<=6;i = i +1)
{
    console.log(i + "  inside the for loop " + (i<=6))
}
console.log(i + "  outside the for loop " + (i<=6));
1  inside the for loop true
2  inside the for loop true  
3  inside the for loop true  
4  inside the for loop true  
5  inside the for loop true  
6  inside the for loop true  
7  outside the for loop false
------------------------------------
var i;
for(i=11;i<=6;i = i +1)
{
    console.log(i + "  inside the for loop " + (i<=6))
}
console.log(i + "  outside the for loop " + (i<=6));
11  outside the for loop false
-------------------------------------
var i=1;
for(;i<=6;)
{
    console.log(i + "  inside the for loop " + (i<=6))
    i = i +1;
}
console.log(i + "  outside the for loop " + (i<=6));
-------------------------------------------------------
var i=1;
for(;;)
{
    console.log(i + "  inside the for loop " + (i<=6))
    i = i +1;
}
// unreachable code
console.log(i + "  outside the for loop " + (i<=6));
//infinite loop
-----------------------------------
var i=1;
for(;;)
{
    console.log(i + "  inside the for loop " + (i<=6))
    if(i==6)
    {
        break;
    }
    i = i +1;
}
console.log(i + "  outside the for loop " + (i<=6));
1  inside the for loop true
2  inside the for loop true 
3  inside the for loop true 
4  inside the for loop true 
5  inside the for loop true 
6  inside the for loop true 
6  outside the for loop true
--------------------------------------------
array ->
	- collection of values 
        - *may be of same type or different type or other arrays 
        - stored in a conitinious memory location
	- indentified by their position called index.
        - index value starts with zero '0' and ends with array size minus one.
          example : array with 9 values 
                    index starts with 0 and ends with 8.
        - index can be string, but it is not reflects the size.
        - all values shares same name.
	- array in javascript created in two ways 
                      -using []
                      -using Array()
        - var arrayname = [val1,val2,val3,......valN];
        - to read a value 
              arrayname[index]
        - to assign a value
              arrayname[index] = value;

array management:
	-creation of array
	-array values management 
                   -add
                   -delete
                   -edit/modify/update
                   -search/find
                   -sort
                   -other
        -array methods

----------------------
var marks = [99,35,45,88,58,69];
console.log(marks[0]);
console.log(marks[1]);
console.log(marks[2]);
console.log(marks[3]);
console.log(marks[4]);
console.log(marks[5]);
99
35
45
88
58
69
---------------------------
var marks = [99,35,45,88,58,69];
console.log(marks[0]);
marks[0] = 89;
console.log(marks[0]);
------------------------------
var marks = [99,35,45,88,58,69];
for(i in marks)
{
    console.log(i + ' value  ' + marks[i]);
}
0 value  99
1 value  35
2 value  45
3 value  88
4 value  58
5 value  69
---------------------------------------------
var marks = [99,35,45];
for(i in marks)
{
    console.log(i + ' value  ' + marks[i]);
}
0 value  99
1 value  35
2 value  45
----------------------------
var marks = [99,35,45,66];
for(i in marks)
{
    console.log(i + ' value  ' + marks[i]);
}
0 value  99
1 value  35
2 value  45
3 value  66
--------------------------------
var marks = [];
for(i in marks)
{
    console.log(i + ' value  ' + marks[i]);
}
------------------------
Creation of an array:
	using []
	using Array()
----------------------------------
var marks = []; // empty array
console.log(typeof(marks)); // object
console.log('size of marks : ' + marks.length);
//size of marks : 0
console.log(marks); //[]
-----------------------------------
var marks = [88,44,99,55,46,39]; // with values - same type
console.log(typeof(marks)); // object
console.log('size of marks : ' + marks.length);
//size of marks : 6
console.log(marks); //[ 88, 44, 99, 55, 46, 39 ]
---------------------------------------------------------
var Product = [9009,'Apple','12pc',199,true]; 
// with values - different type
console.log(typeof(Product)); // object
console.log('size of Product : ' + Product.length);
//size of Product : 5
console.log(Product); 
//[ 9009, 'Apple', '12pc', 199, true ]
-----------------------------------------
var Student = [1009,'John Miller','MERN','17/03/2025','Adilabad',18000.00,true];
console.log(Student);
console.log('size : ' + Student.length);
------------------------------------------
var FoodItem = 
[
    2009,
    'Butter Masala Dosa',
    125,
    4.1,
    2194,
    'Best Seller',
    'Veg',
    true,
    'Butter-Masala-Dosa.jpg'

]
console.log(FoodItem);
console.log('size of FoodItem : ' + FoodItem.length);
---------------------------------------------------------
https://www.bigbasket.com/media/uploads/p/m/40072494_12-bb-royal-organic-turtoor-dal.jpg?tr=w-154,q-80
-----------------------------------------------------------------------------------------------------
var Product = 
[
    9001,
    'Organic Toor/Arhar Dal',
    'bb Royal',
    '4',
    '20245 Ratings',
    'Veg',
    '41% OFF',
    '500g',
    '1 kg',
    '2 kg',
    '29%',
    '41%',
    '33%',
    150,
    299,
    589,
    105.93,
    177.21,
    393.03,
    true,
    true,
    true,
    '40072494_12-bb-royal-organic-turtoor-dal.jpg',
    true
];
console.log(Product);
console.log('size of Product: ' + Product.length);
------------------------------------------------------
Product
	-ProductId - only one value 
        -Name - only one value
        -BrandName - only one value
        -TypeOfProduct -only one value
        -Rating - only one value
        -RatingBy - only one value
        -Quantity - multi valued property
        -Mrp - multi valued property
        -Discount - multi valued property
        -SalePrice - multi valued property
        -IsAvailable - multi valued property
        -ImagePath - only one value
        -Status - only one value

Number of properties : 13
Number of values : 23
Note: to handle 23 values by using 13 properties 
--------------------------------------------
var Quantity = ['500g','1 kg','2 kg'];
var Mrp = [150,299,589];
var Discount = ['29%','41%','33%'];
var SalePrice = [105.93,177.21,393.03]
var QtStatus = [true,true,true]
var Product = 
[
    9001,
    'Organic Toor/Arhar Dal',
    'bb Royal',
    '4',
    '20245 Ratings',
    'Veg',
    '40072494_12-bb-royal-organic-turtoor-dal.jpg',
    true,
    Quantity,
    Mrp,
    Discount,
    SalePrice,
    QtStatus
];
console.log(Product);
console.log('size of Product: ' + Product.length);
------------------------------------------------------------------
var Quantity = ['500g','1 kg','2 kg'];
var Mrp = [150,299,589];
var Discount = ['29%','41%','33%'];
var SalePrice = [105.93,177.21,393.03]
var QtStatus = [true,true,true]
var Product = 
[
    9001,
    'Organic Toor/Arhar Dal',
    'bb Royal',
    '4',
    '20245 Ratings',
    'Veg',
    '40072494_12-bb-royal-organic-turtoor-dal.jpg',
    true,
    Quantity,
    Mrp,
    Discount,
    SalePrice,
    QtStatus
];
console.log(Product);
console.log('size of Product: ' + Product.length);
console.log('Name  :' + Product[1]);
console.log('Brand :' + Product[2]);
console.log("Rating :" + Product[3]);
console.log("Rating Given By : " + Product[4]);
console.log('Type of Product : ' + Product[5]);
console.log('Image path : ' + Product[6]);
console.log('Product is available : ' + Product[7] );
console.log("Quantity : " + Product[8])
console.log('1st Quantity  : ' + Product[8][0] )
console.log('1st Mrp  : ' + Product[9][0] )
console.log('1st Discount  : ' + Product[10][0] )
console.log('1st SalePrice  : ' + Product[11][0] )
------------------------------------------------------
creating an array by using Array()

var marks = Array(); // empty array
console.log(marks);
console.log(marks.length);
-------------------------------
var marks = Array(9); // array with single value
console.log(marks);   // creates array with the given size
console.log(marks.length);
-------------------------------------------
var marks = Array(99,44,77,88); // array with multiple values
console.log(marks);   
console.log(marks.length);
----------------------------
var Quantity = Array('500g','1 kg','2 kg');
var Mrp = Array(150,299,589);
var Discount = Array('29%','41%','33%');
var SalePrice = Array(105.93,177.21,393.03);
var QtStatus = Array(true,true,true);
var Product = 
[
    9001,
    'Organic Toor/Arhar Dal',
    'bb Royal',
    '4',
    '20245 Ratings',
    'Veg',
    '40072494_12-bb-royal-organic-turtoor-dal.jpg',
    true,
    Quantity,
    Mrp,
    Discount,
    SalePrice,
    QtStatus
];
console.log(Product);
console.log('size of Product: ' + Product.length);
console.log('Name  :' + Product[1]);
console.log('Brand :' + Product[2]);
console.log("Rating :" + Product[3]);
console.log("Rating Given By : " + Product[4]);
console.log('Type of Product : ' + Product[5]);
console.log('Image path : ' + Product[6]);
console.log('Product is available : ' + Product[7] );
console.log("Quantity : " + Product[8])
console.log('1st Quantity  : ' + Product[8][0] )
console.log('1st Mrp  : ' + Product[9][0] )
console.log('1st Discount  : ' + Product[10][0] )
console.log('1st SalePrice  : ' + Product[11][0] )
---------------------------------------------------------
Read a value 
    arrayname[index]
Assign a value
    arrayname[index]=value;
--------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log(marks);   
console.log(marks.length);
console.log(marks[0]); // valid index values 0 to 8
console.log(marks[35]); // undefined
Note: value from a non-existing index becomes undefined
---------------------------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log(marks);   
console.log(marks.length);
console.log(marks[0]); // valid index values 0 to 8
marks[0] = 69;
console.log(marks[0]);
console.log(marks);
marks[12] = 8;
console.log('size : ' + marks.length);
console.log(marks);
//Note: when value assinged to a non-existing index
//memory is allocated with the given index.
--------------------------------------------------
var Product = []; // empty 
console.log(Product);
console.log('size : ' + Product.length);
Product[0] = 9009;
console.log('size : ' + Product.length);
Product[1] = 'Apple';
console.log('size : ' + Product.length);
Product[2] = '1Kg';
console.log('size : ' + Product.length);
Product[3] = 199.99;
console.log('size : ' + Product.length);
console.log(Product);
---------------------------------------
var Product = [];
console.log(Product);
Product['ProductId'] = 9009;
Product['ProductName'] = 'Green Mango';
Product['Quantity'] = '1Kg';
Product['Price'] = 99;
console.log(Product);
console.log('size : ' + Product.length); // 0
console.log(Product['ProductId']);
console.log(Product['ProductName']);
console.log(Product['Quantity']);
console.log(Product['Price']);
output
[]
[
  ProductId: 9009,
  ProductName: 'Green Mango',
  Quantity: '1Kg',
  Price: 99
]
size : 0
9009
Green Mango
1Kg
99
-------------------------------
Array methods
	-add and remove 
         -push() : used to append the given value/values/array at the end of the array and 
                   it returns the new size of the array.
	 -unshift() - used to insert the value at the start of an array and returns the new size
         -pop() - used to remove the value from end of an array. 
                  It returns the removed value.
         -shift() - used to remove and return the value from the top/starting of an array.


var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.push(49)); // with single value
console.log(marks);
--------------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.push(49,19,29)); // with multiple value
console.log(marks);
--------------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.push([49,19,29])); // with array
console.log(marks);
--------------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.unshift(49)); // with single value
console.log(marks);
------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.unshift(49,19,29)); // with multiple value
console.log(marks);
-------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.unshift([49,19,29])); // with array
console.log(marks);
--------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.pop()); // removes and returns the end value
console.log(marks);
console.log('size ' + marks.length);
-------------------------------------
var marks = [99,44,77,88,11,89,23,95,59,[19,29,39]]; 
console.log('size ' + marks.length);
console.log(marks.pop()); // removes and returns the end value
                        // here the last value is array
console.log(marks);
console.log('size ' + marks.length);

----------------------------------------------------
var marks = [99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.shift()); // removes and returns the start value
console.log(marks);
console.log('size ' + marks.length);
-----------------------------------------
var marks = [[12,23,29],99,44,77,88,11,89,23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.shift()); // removes and returns the start value 
                            // which is an array
console.log(marks);
console.log('size ' + marks.length);
------------------------------------------
var marks = [23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.pop());
console.log('size ' + marks.length);
console.log(marks.pop());
console.log('size ' + marks.length);
console.log(marks.pop());
console.log('size ' + marks.length);
console.log(marks);
console.log(marks.pop()); // undefined
--------------------------------------
var marks = [23,95,59]; 
console.log('size ' + marks.length);
console.log(marks.shift());
console.log('size ' + marks.length);
console.log(marks.shift());
console.log('size ' + marks.length);
console.log(marks.shift());
console.log('size ' + marks.length);
console.log(marks);
console.log(marks.shift()); // undefined
Note: pop()/shift() on empty array returns undefined.
---------------------------------------------