How to declare Block-Scoped Variables in JavaScript?

JavascriptWeb DevelopmentObject Oriented Programming

To declare block scoped variables, we use the keyword let and const introduced in ES2015.

Following is the code showing declaring black scoped variables in JavaScript −

Example

 Live Demo

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .result,.sample {
      font-size: 20px;
      font-weight: 500;
   }
</style>
</head>
<body>
<h1>Declaring block scoped variables</h1>
<div class="sample"></div>
<div style="color: green;" class="result"></div>
<button class="Btn">CLICK HERE</button>
<h3>Click on the above button to declare and display block scoped variables</h3>
<script>
   let resEle = document.querySelector(".result");
   let sampleEle = document.querySelector(".sample");{
      let a = 22;
      const b = 44;
      sampleEle.innerHTML = "let a = " + a + "<br>";
      sampleEle.innerHTML += "const b = " + b + "<br>";
   }
   document.querySelector(".Btn").addEventListener("click", () => {
      try {
         a + b;
      }
      catch (err) {
         resEle.innerHTML = "a+b = " + err;
      }
   });
</script>
</body>
</html>

Output

The above code will produce the following output −

On clicking the ‘CLICK HERE’ button −

raja
Published on 16-Jul-2020 08:13:02
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