scope, closure, execution context(class-7)

//Execution context
//javascript scope
//javascript closure
//javascript hoisting
//Visualization (all)

//Execution context

  //global (outside of function)

  //functional (inside of a function)





/////////// global

//   const num1 = 10
//   const num2 = 20
// functional execution context
//   function add(){
//     return num1 + num2
//   }

//   console.log(add())

//  /// functional execution context
//   function subtract(){
//     return num1 - num2
//   }
//   console.log(subtract())


//   /////



//scope
  //global scope (outside of function)

  //functional scope (var)
  //block scope(ES6) enclosed by  {}


//global
// const a = 10


//block scope ( applicable for let, const)
//   if(true){
//     var d = 20
//     const c = 30
//   }

//   console.log(d)

// //   console.log(c)

//  function sum (){
//      //local
//      const b = 10
//      var e = 20

//     //  console.log(f)
//      function inner(){
//         const a  = 100
//        console.log(a)
//        const f = 20
//      }
//      inner()
//     console.log(a)
//  }


 //not accessible (local scope)
// console.log(e)

//  sum()



//closure scope

// function greet(greetings){
//     //greetings = 'hello'
//  return name =>{
//      //name  = 'samim'
//     return greetings + ' ' + name
//  }
// }


// const secondFn = greet('hello')

// console.log(secondFn('samim'))
// console.log(secondFn('samim'))




//javascript hoisting

// console.log(a) //temporal dead zone
// console.log(x)
// console.log(sum(10, 20))
// console.log(subtract(20, 10))

// const  a = 10
// var x = 20


// function sum(num1, num2){
//     return  num1 + num2
// }
// console.log(sum(10, 20))

// var subtract = function (num1, num2){
//     return  num1 - num2
// }

// console.log(subtract(20, 10))

// console.log(a)



//Hoisting
//creation stage
//variable declaration
//take function statement in memory


//execution stage
//variable value assignment
//calling (run)


//creation stage
// var x;
// var a;
// function sum(num1, num2){
//    return  num1 + num2
// }

// var subtract;


// //execution stage
// console.log(a)
// console.log(x)
// console.log(sum(10, 20))
// console.log(subtract(20, 10))

// var a = 10
// var x = 20

// a = 10
// x = 20
// subtract = function (num1, num2){
//    return  num1 - num2
// }
// console.log(subtract(20, 10))

// console.log(a)



//var let const

//var- attached with window, re-declaration, Hoisting, functional scope
//let - Not attached with window, No hoisting(?), no re-declaration but can be re-assigned can be  block scope
//const - same as let,  can't be re-assigned