Lexical Scope JavaScript

• What is a Scope?

  • A Scope refers to the current context of your code.
  • It can be either locally or globally defined.
  • ES6 gives block scope as well.
  • Block scope.
  • Function scope.
  • Global scope.

• What is a Lexical Scope?

  • A variable defined outside a function can be accessible inside of another function defined after a variable declaration, but the opposite is not true.

• Example 1

// global scope
var username = "Chaitanya";

function local() {
	// local scope
	console.log(username);
}

local(); // Chaitanya

// global scope

function local() {
	// local scope
	var username = "Chaitanya";
}
console.log(username); // undefined

local(); 

• Example 2: Closures Javascript

// global scope

function subscribe() {

	// inner scope 2
	var name = "Chaitanya";

	function displayName() {
		// inner scope
		alert(name); // Chaitanya, [[Closures Javascript]]
	}

	displayName();
}

subscribe(); // alert with Chaitanya