2 notes.txt

Content:

1.Variables,variable types 
2.operators
3.Data types
4.Type conversations

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1.Variables:

What is variables?
===>It is a name given to  memory location.
// oru  value ஐ store seiya kudiya container than  variables aagum.

===>It is case sensitive i.e   ===> a != A

===>Alphabetic letters are only used.not consider to special characters.

===>SYNTAX:
var/let/const         variablename      =  ;
(keyword)            (user defined)  (mandatory)

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===>VARIBLES 3 types :
1.var    2.let   3.const

var:

*ES5 (old version).
*redeclare and reassign.
*global  scope.

*Example:
var a=10;
var a=20;
console.log(a);    // output : 20

let:

*ES6 (new  version).
*cannot redeclare but can reassign.( reassign only)
*block scope.

*Example:
let  a=10;
      a=20;
console.log(a);    // output : 20 
// values I only reassign pannalam.marubadiyum let redeclare panna mudiyathu.

constant:

*ES6 (new  version).
*cannot redeclare and reassign.fixed the input.
*block scope.

*Example:
const  a=10;
console.log(a);    // output : 20

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2.What is Operators?

===>operators performed specific operations.

====>different types of operators in java

1.Arithmetic operator : +   -   *    /   %

2.Assignment operator : =

3.Logical operator : &&  AND operator ===> Must two conditions satisfied AND operator is working.
                     || OR operator   ===> If one conditions satisfied OR operator is working.
                     != Not Equal To  ===> opposite to Equal To

4.Conditonal or Comparison operator : < Greator than
                                      <=Greator than Equal to
                                      <Less than
                                      <=Less than Equal to
                                      == Double Equal To   ===> Checking Two or more inputs are same using this opearator.
                                      === Thriple Equal To ===> Checking same the number and the data types.

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3.Data types:

What is data types?

===>Data types specify the different sizes and values that can be stored in the variable.

===>A data type in Java represents the size and different values that can be stored in a variable.
    //variables I store panni vaikka kudiya values in type solluvathu than data types aagum.

===>Different types of data types includes in javascript

1.Number  ===> 1 2 3 4 /  5.5
2.String  ===> “ ”  /  ' '                        ===> using single or double quotes.
3.Boolean ===> True / False
4.Array   ===> [ 1234,”WELCOME“,true/false, {}  ] ===>  using square brackets.

5.Object  ===> represented in key value pairs.
              {
                key : value
              }                                   ===> using curly braces.

6.NaN     ===> Not A Number 

  Example:
  var a= "prabha";
  var b = +"prabha";
  console.log(b);  //NaN
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4.Type Conversions

What is type Conversions: 

===>The process of converting data of one data type into another.
 
===>Converting one primitive datatype into another
   //oru data type I vera oru data type aaga maatra payanpaduthu
   
===>Type conversions have 3 methods.

    (1) + or parseInt   ===> string to number.

    Example:
           var a = "12345";
           var a = +"12345"   //parseInt("12345")
           var b = "67890";
           var b = +"67890";  //parseInt("67890")
           var c = a+b;
           console.log(c);    // 80235

    (1.1) ParseFloat      ===> string decimal value change to number.

    Example:
           var a = "12.3";
           var a = parseFloat("12.3");
           var b = "67.8";
           var b = parseFloat("67.8");
           var c = a+b;
           console.log(c);    // 80.1

      (2) Normal ஆக ஒரு Number ஐ String ஆக மாற்ற:
       ***toString*** இன்னொரு வழி:

      Example:
            var a = 1 + "1"         //concat
            console.log(a);
            console.log(typeof(a)); //11 String
      

      (2.1) Array Number ஐ String ஆக மாற்றும் வழி:
      Example:
           var b=[1,2,3];
           console.log(b.toString());  // output: “1 , 2 , 3”         
      

      (3) Boolean to String :

      Example:
            var a = true;
            console.log(String(a));
            console.log(typeof(a));    // true   boolean ===>இவ்வாறு கொடுக்கும்போது type சரியான முறையில் வரவில்லை.
 
      இப்படி கொடுத்தால் தான் சரியான முறையில் type ஐ கண்டுபிடிக்க முடியும்.
            var a = true;
            var b = String(a)
            console.log(String(a));
            console.log(typeof(b));    // true   string


      (3.1) Boolean to Number :

      Example:
            let a = 0;
            let b = Number(a);
            console.log(Boolean(a));
            console.log(typeof(b));    // false  number
  
      Example2:
            let a = 1;
            let b = Number(a);
            console.log(Boolean(a));
            console.log(typeof(b));    // true  number    
      ===> பூஜ்ஜியத்தை தவிர எந்த number ஐ கொடுத்தாலும் அது true ஆகத்தான் காட்டும்.


      (3.2) Boolean to "0"   ""    []  :

      Example:
            let a = "0";     ===>ஏதேனும் ஒரு number including "0" இருந்தாலும் கூட true ஆக வரும்.
            let b = String(a);
            console.log(Boolean(a));
            console.log(typeof(b));    // true string

      Example2:
            let a = "";      ===>empty string ஆக கொடுக்கும் போது false ஆக வரும்.
            let b = String(a);
            console.log(Boolean(a));
            console.log(typeof(b));    // false string

      Example3:
            let a = [];      ===>empty Array ஆக கொடுக்கும் போது true ஆக வரும்.
            console.log(Boolean(a));   // true 
      
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