JavaScript has feature called Scope. it is not simple as you think ,many developers are confuse till now. i'll try my best to understand scope in javascript.

What is Scope ?

• Scope is the accessibility of variables, functions and objects in some particular part of your code during runtime.

Scope in JavaScript :

• in JavaScript there are two types of scopes :
  • Global Scope
  • Local Scope

Local Scope : Variable which is define within function , variable has local scope.

Global Scope : Variable which is defined outside of function, variable has global scope.

Global Scope :

• When you start writing JavaScript in a document, you are already in global scope.
• a variable has global scope, it written outside a function.

let name = "Akshar"; //by default global scope.

• If variable has global scope, we can use the variable inside a function also. for Example :

let name = "Akshar"; //it has global scope
console.log(name) // Akshar

function printName(){
      console.log(name); //Akshar
}
printName( );

Local Scope :

• Variable defined within a function it called local scope.
• for example :

//global scope function
function globalFunction(){
      // local scope function
      function otherFunction(){
       // code 
      }
}

Block Statement :

• Block statements like if and switch has block scope.
• if we have create variable inside block statements a variable has block scope.
• for Example :
• only var keyword support a declaration in block scope.

  if(true){
    var name = "Akshar";
  }
  console.log(name) //Akshar
  

• let and const keyword does not support declaration in block scope, for example :

if(true){
    //var keyword has global scope by default and also block scope
    var name = "Akshar"; // Akshar
    //let keyword doesn't have block scope.
    let likes = "coding"; //ReferenceError
    //const keyword doesn't have block scope.
    const skills = "Javascript"; //ReferenceError
}
console.log(name);
console.log(likes);
console.log(skills);