Understanding const, let, and var in JavaScript

Explanation:

In JavaScript, we use const, let, and var to create variables—those special boxes we talked about. But each one works a little differently, like different types of containers for different jobs.

1. var: This is the oldest way to create a variable. It can be used anywhere in the program, even outside the place where it was created. It’s like a box that can be seen

2. let: This is a newer way to create a variable. It can only be used in the specific area where you created it. Think of it like a box you put in a drawer—it can’t be seen outside that drawer.

3. const: This is another way to create a variable, but it’s special because you can’t change what’s inside the box after you create it. It’s like a sealed jar; once you close it, you can’t take anything out or put anything else in!

Code Example 1 (Using var):

var name = "Satyendra"; // This is a var variable
if (true) {
    var name = "Alice"; // This reuses the same variable
    console.log(name); // Output: Alice
}
console.log(name); // Output: Alice (changed outside the block)

Explanation for Code Example 1:

Here, we first create a var variable called name with the value "Satyendra." Inside the if block, we use var again to change name to "Alice." When we log name outside the block, it shows "Alice" because var can be accessed from anywhere, even outside the block where it was changed.

Code Example 2 (Using let):

let age = 10; // This is a let variable
if (true) {
    let age = 15; // This creates a new variable just for this block
    console.log(age); // Output: 15
}
console.log(age); // Output: 10 (the original value remains unchanged)

Explanation for Code Example 2:

We create a let variable called age with the value 10. Inside the if block, we create a new age variable that only exists inside this block and set it to 15. When we log age inside the block, it shows 15, but outside the block, it still shows 10 because let keeps it safe inside its drawer.

Code Example 3 (Using const):

const pi = 3.14; // This is a const variable
console.log(pi); // Output: 3.14

// pi = 3.14159; // This would cause an error because we can't change const variables

Explanation for Code Example 3:

We create a const variable called pi and give it the value 3.14. When we try to log pi, it shows 3.14. If we try to change pi later, like setting it to 3.14159, it will cause an error! This is because const means we can’t change what’s inside the box once we seal it.