Scope

In JavaScript, scope refers to the visibility of variables ,Where you can access a specific variety of Function in our code. Scope is Directly depending on lexical Environment. Javascript has the following kind of Scope .

1. Global scope
2. Local scope -- Block scope -- Function scope

Global Scope

Variables defined outside any function, block, or module scope have global scope. Variables in global scope can be accessed from everywhere in the application.

let  person = 'Kavita';
 function display() 
{
    console.log(person); //kavita
 }
 console.log(person);//kavita

In JavaScript, a variable can also be used without declaring it. If a variable is used without declaring it, that variable automatically becomes a global variable.

function greet() {
    a = "hello"
}

greet();

console.log(a); // hello

Local scope

when we define some variables inside curly brackets {} or inside a specific function then those variables are called local variables .The local scope was further broken down into two different scopes: Function scope and Block scope.

Function Scope

Variables defined inside a function are not accessible from outside the function.

let a=5;

function add(){
 let b="hello"
console.log(a+b); //5hello
}
add();
console.log(a+b);error

Block Scope

The variable declared inside the curly brackets { and } can be treated as block scope. Variables declared with let and const can have block scope.These curly brackets can be of loops, or conditional statements, or something else.

let a=4;
 {
let a=8;
}
console.log(a);//4