Hoisting in JavaScript -

 

Hoisting occurs because JavaScript engine will compile the code before its interpretation. The compiler actually considers var a = 2; as two different statements var a; and a = 2;. So the part of the compiler finds all the declaration first and then associate their assignment with their appropriate scopes.

* Hoisting is Javascript`s default behavior of moving declarations to the top

* JavaScript Declarations are Hoisted

* It can not work on let / const

* In anonymous function also, it can not work

Declaration - Assigning & Initialization

Declaration : (Hoisted)

- Declaration means simply giving a name to the and it`s data type ( by default Global without data type).

- we can`t see their value until we invoke/ call it.

Ex:

    var a;

    function a(){}

Assigning :

Assigning means simply storing the value in a variable.

Ex :

    a = 5 ;

Initialization : (Not Hoisted)

It means both declaring and assigning a intial value.

Ex :

    var a=5;


    Variable Hoisting..

     * Scope Means availability, and place  of the variables

    <script>

        // Variable Hoisting

        // console.log(abc);

        // console.log(msg);

        var abc = 99;

        var msg = 199;

        console.log(abc);

        console.log(msg);

    </script>

    Function Scope & Function Hoisting..
          <script>

        console.log(abc);

        function ramesh(){

            var abc = 99;  

            console.log(abc);  

        }

        ramesh();

        console.log(abc);

    </script>

        Block Scope..    <script>

        // Block Scope

        {

        const abc =999;  // let,const will not work on block scope

        var msg = 799;

        //console.log(abc);

        }

        console.log(abc);

    </script>