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Scope in Javascript

Scope in Javascript

Scope of var, let, and const

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Mohammad Bilal Mansuri
·

2 min read

Scope

The scope can be defined as the region in which a variable can be accessed. Outside this region, that variable is not available. In JavaScript, there are three types of scopes

  • Block Scope,
  • Function Scope,
  • Global Scope

Block Scope -

Block scope is the scope between two brackets { },

{
let x  = 10;
}
// x cannot be accessed here.

Function Scope -

Each function creates a new scope on its own called function scope.

function minimize(){
  let x = 10;
//x can be accessed here
}
// x cannot be accessed here

Global Scope -

Variables declared Globally (outside any function) have Global Scope.

let x = 2;
var a = 3;
const b = 1;

{
// x, a, b all three can be accessed here
}
function print(){
console.log("This is a function");
// x, a, b all three can be accessed here
}

Scope of var, let, and const

Var is globally scoped, it can be accessed anywhere no matter where it is declared.

{
    var a = 10;
}
console.log(a); //output will be 10

Let and Const are block-scoped, they can be accessed only inside the block they are declared in.

{
    let a = 10;
    const b = 20;
    console.log(a, b); // output will be 10,20
}
console.log(a, b); //error

Output-

image.png

Conclusion -

This was a short summary on scope in JavaScript, you can learn more about scopes in MDN docs. Scopes help to understand the variable shadowing. I will be explaining shadowing in my next blog.

JavaScriptScope