Block Scoping in JavaScript.

JavascriptWeb DevelopmentObject Oriented Programming

Block scope is an area between two { curly braces } which can be between loops, if condition or switch statement. The let and const introduced in ES2015 allow us to create block scoped variables that can be accessed only inside those block.

Following is the code showing block scoping in JavaScript −


 Live Demo

<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
      font-size: 20px;
      font-weight: 500;
<h1>Block scoping in JavaScript</h1>
<div style="color: green;" class="result"></div>
<button class="Btn">CLICK HERE</button>
<h3>Click on the above button to access variable inside and outside the block</h3>
   let resEle = document.querySelector(".result");
   document.querySelector(".Btn").addEventListener("click", () => {
      let b = 44;{
         let a = 22;
      resEle.innerHTML = 'Accessing variable inside its block b = ' + b + '<br>';
         resEle.innerHTML += 'Accessing variable outside its block a = ' + err;


The above code will produce the following output −

On clicking the ‘CLICK HERE’ button −

Published on 16-Jul-2020 11:21:03