Defending variables in JS have its own way.

We have three ways to defend a variable let, var, const.

We mostly use let because of the block scope which I'll explain in the below. 👇🏻

Let

The keyword let makes a variable only useable within the scope it made in, you can't use it outside that scope.

E.g.

{
    let num = 10;
    console.log(num); // Outputs: 10
}
console.log(num); // ERROR

Var

The keyword var makes a global variable, you can use it everywhere in the code.

E.g.

{
    let num = 10;
    console.log(num); // Outputs: 10
}
console.log(num); // Outputs: 10

Const

The keyword const makes an unchangeable variable, you can't change its value.

E.g.

const pi = 3.14159265359;
pi = 4; // ERROR