Variable Declaration using (var, let, const)

var was the original way to declare variables in JavaScript, but in recent versions of the language, let and const have been introduced as alternative ways to declare variables with different scoping and immutability behaviors.

Here are the main differences between let, var, and const:

var

Variables declared with var have function-level scope. This means that they are accessible within the function they are declared in, as well as any nested functions.

let

Variables declared with let have block-level scope. This means that they are accessible only within the block they are declared in, including any nested blocks.

const

Variables declared with const have block-level scope and are immutable. This means that they cannot be reassigned to a different value after they are initialized.

Here are some examples of var, let, and const declarations without using functions:

// var example
var x = 10;
if (true) {
  var x = 20;
}
console.log(x); // Output: 20

// let example
let y = 10;
if (true) {
  let y = 20;
}
console.log(y); // Output: 10

// const example
const z = 10;
if (true) {
  const z = 20;
}
console.log(z); // Output: 10